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Frequently Asked Questions

Q. I have a natural stone substrate which needs to be sealed. What do I use?

A. Many products contain oil or plasticizers that will penetrate into porous substrates, like natural stone. Applying these products will result in a dark edge around the seal, contamination. This contamination cannot be removed or reversed. We recommend to apply the Bostik S955 SEAL’N’FLEX NON-STAINING, Bostik S960 SILICONE NON-STAINING or the Bostik H750 SEAL’N’BOND PREMIUM, to avoid contamination and to offer you the ability to seal the natural stone. For more information please read the FactSheet FS012 Suitability and pre-treatment of surfaces.

Q. Do I need to use a primer before sealing?

A. It is recommended in almost all situations, especially when you are dealing with porous substrates. For more information please read the FactSheet FS012 Suitability and pre-treatment of surfaces.

Q. What is the correct dimension of the joint sealant?

A. The correct dimension of a joint sealants until 10mm is 1 on 1 (eg.5 mm in width and 5 mm in depth)You’re your joint width is broader than 10mm you can easily calculated the right dept by using the following calculation;

Correct dept = Joint width mm / 3 + 6mm (eg. Joint width 21mm/3+6mm = 13mm depth)

Bostik provides several products in different technologies were a joint width of maximum 40mm can be applied. An durable joint sealant is depending on the movement of the adjacent building elements and the use of a correct backer rod. For more information please read the FactSheet FS008 Joint Dimensions.

Q. What is meant by an expansion joint?

A. A construction joint that will expand and compress during its lifetime, absorbing the natural movement of a building/wall (dilatation).

Q. What is meant by a connection joint?

A. Joints between building materials with an aesthetical character. Joints around ceilings, stairs, frames, base,- and skirting boards etc.

Q. What is meant by a construction joint?

A. Joints which are required to bond and absorb movement between different kind of building materials such as sheet material, container-construction, trucking & trailers etc. but also in general construction (Prefab). 

Q. What is meant by a glazing joint?

A. Joints that seal single or insulating glass with various frames and surfaces, think of primed/painted wood, aluminum and/or plastic frames etc. These sealants should be an elastic sealants such as a silicone, polyurethane or hybrid sealants. Paintable and UV resistant is of the essence.

Q. What types of backing rods are available for a good, solid and durable sealing?

A. Two types of backing rods are available. One is a PE (polyethylene) product that provides a closed cell structure and there is a PU (polyurethane) product that provides an open cell structure.

Q. When do we advise Backing rods?

In general, backing rods are advised to create a correct joint dimension in a construction joint, often expansion or connection joints. The PE (polyethylene) quality with closed cell structure is recommended in joints where a high degree of mechanical load is expected (often horizontal joints for pedestrian walkways or warehouses etc.). The PU (polyurethane) quality with open cell structure is often recommended where mechanical ballasting is less important, for instance expansion joints in facades.

Q. What is a curtain wall?

A. A curtain wall is a non-load-bearing facade or partition between the exterior and interior of a building. Because the curtain wall is non-load-bearing, it can be constructed from light materials, such as glass or sheet material which saves on weight.

Q. Can I paint silicone sealants?

A. No, paint does not adhere to a silicone sealant. If you need to paint the sealant after application, we highly recommend to use the Bostik H775 GLASS’N’SEAL PREMIUM PAINTABLE in glazing and façade joints. For more information please read the FactSheet FS006 Tolerance of sealants with paints.

Q. I have painted my acrylic sealant but it cracks right in the middle on all joints?

A. This is reoccurring compliant that happens every once in a while. Reason why this phenomenon occurs is that during curing acrylic joint will show shrinkage because of evaporation of water which is part of all acrylic formulations. If you overpaint the acrylic joint to soon full retraction of joint isn’t complete yet and paint isn’t flexible enough to withstand this deformation, causing cracking of the paint. If you look closely the sealant isn’t cracked only the paint.

Q. I have painted a Hybrid and my solvent based paint won’t dry?

A. With the application of hybrids which are to be painted you should be aware that solvent based (synthetic) paints can show a curing delay. Bostik H775 GLASS’N’SEAL PREMIUM PAINTABLE is a unique formulation within the hybrid product group which is fully paintable with synthetic and water based paints.

Q. Are there sealants that can be painted over immediately, I wish to continue painting the same day?

A. Yes, it exists in our range this is the Bostik A980 INSTANTLY PAINTABLE. It is a unique formula, the only acrylic sealant that is really directly paintable.

Q. I just became the new owner of an existing house and I have all kinds of cracks and holes in my wall and ceiling?

A. For this you can use our Bostik A930 Using EASY FILLER PRO. An Ultra-lightweight filler that shows no shrinkage based on acrylic, so that it can be painted over with all possible paints.

Q. How much time do I need before I can paint over an acrylic sealant?

A. Standard acrylic sealants do not have a standard curing time, it depends on variables such as; Air humidity,

Temperature, Humidity of substrate and the dimension of the joint. In the worst case scenario it can take up to several days. In general If you are in an environment with normal variables we recommend that you take 24 hours into account before overpainting the acrylic sealant.

Q. Are all paints compatible with Bostik Acrylics?

A. it is impossible for us to test all paints and paint qualities on our acrylic products. If your product has the Bostik UCA logo on the packaging, then you have a quality product from Bostik that has tested compatibility with the paint producing industry, but always carry out your own test to be sure.

Q. Can I use an acrylic outside?

A. Despite the fact that an acrylic sealant is water-based, you can use almost all acrylic sealants outside, but only suitable when youestimate a long dry period, otherwise the sealant will dissolve slightly when it rains. If you want to avoid this, you can use our Bostik A750 EXTERIOR ACRYLIC, this acrylic sealant is a high quality acrylic sealant which is rain resistant after application.

Q. Can I use and acrylic sealant for glazing?

A. No, unfortunately that is not possible, acrylic sealants do not have the same movement capability as a glazing sealant (elastic sealant). That is why acrylic sealants are never certified with a CE marking for glazing (CE EN 15651-2)

Q. How elastic or flexible is an acrylic?

A. An acrylic sealant is a plastic-elastic sealant and has a maximum movement capacity of 12.5%. this means that a high quality acrylic sealant can absorb constantly movement up to 12.5%. If the joint has a larger movement capability the acrylic sealant will tear at a later time, but this can take months before this becomes visible. In that case it is better to use a hybrid sealant when higher movement capability and paintability is a necessity.

Q. What is passive house means?

A. Passive House is a building standard developed by Dr. Wolfgang Feist and Bo Adamson. A passive house is more than energy neutral or energy efficient. A passive house is truly energy efficient, comfortable and affordable at the same time.A passive house can save energy for space heating/cooling up to 90% of a typical building and 75% compared to an average new building.

Q. What is meant by Airtightness?

A. All building elements comply with regulations. Also building elements in passive houses and energy-neutral buildings. In order to maintain the comfortable indoor climate (warm/cool), priority number one is the assure that this indoor climate is not able to escape to the outdoor climate. Otherwise we have to use a lot of energy to maintain the indoor climate. Using energy is not infavour for the environment. Therefore priority number one is to close all connections between all building elements and make them airtight. In other words, seal all possible connections in the outer shell of a building in such a way that the initially introduced energy/warmth  can be enjoyed for as long as possible.

Q. How is airtightness in a building measured?

A. Air tightness is measured using a blower door test. A large fan is placed in the front door completely sealing the door and creates a pressure difference (50Pa) between the inside and the outside of the house. After initiated this test an air loss result can be defined.

Q. How can I detect any air leaks in the outer shell of the building?

A. Air leaks in the outer shell of the building can be detected using blower door tests, thermographic scans and ultrasonic tests. A smoke test can provide a solution for blower testing. In thermographic testing, a display is produced where red areas indicate where energy/warmth is escaping and blue areas where air tightness is OK. In ultrasonic testing, a high-frequency sound is produced by a device and when the mounted building part (eg. Door or window frames) is checked and there is an air leak in the connection, the device makes a sound, if not everything is okay and the component is airtight.

Q. Are there products within the Bostik range that are suitable for airtight construction?

A. Bostik produces many products that are extremely suitable for use in airtight projects. Besides  the well-known Bostik adhesives, sealants and PU FoamsBostik also supplies compression tapes and foils. Or in other words the one-stop-shop for all your airtight questions or solutions.

Q. I read sD-Value, what is meant by that?

A. The sD-value is the equivalent of the air tight thickness layer and thus the resistance to air mass transmission through a material and the notification is in m (meters).

Q. In relation to sD-Value I notice an μ-value quit often, what is this?

A.The μ-value is the vapor diffusion resistance, the resistance offered by a material to the transmission of vapor. To calculate an sD-value we need the μ-value therefore you’ll read these two values in accordance with each other.

Q. What’s The lambda value?

A. The lambda value is display as λ-Value. The lambda value indicates the thermal conductivity of a material. It is expressed in W/mK. The higher the value, the better the heat is conducted and thus the less the material insulates.

Q. I have applied your PU Foam but the product just falls out of the joint I want to fill?

A. This is probably caused by unfavorable circumstances. A lack of moisture (very low air humidity) leads to inefficient curing of the foam and to poor final properties. So always pre moisture the surface/joint with a plant sprayer apply your Bostik PU Foam and after application moisture one more time.

Q. I have a can of PU Foam when activated the PU Foam doesn’t comes out?

A. In that case you can of PU Foam was stored in a lying position which allows the solids in the can to clog the valve and activation isn’t possible anymore. Always store cans upright between +5°C and +25°C to avoid stuck valves. Do not try to activate the valve by means of excessive opening of the valve with nails, screwdrivers etc. bring your canister back to your distributor and request a working substitute.

Q. I have used a gun grade PU Foam but after an hour and a cup of coffee my gun wasn’t working properly anymore.

A. Normally nothing would happen if you put away the can with the gun attached, we suspect that after use the end of the gun has not been cleaned with PU Foam Cleaner. This allows residues of PU Foam to harden and partially or completely clog the gun as a result.

Q. Can I paint over PU Foam?

A. Yes painting of PU Foam is possible. is mainly used in high system ceilings where connections are finished with PU Foam.

Q. Is PU foam UV resistance?

A. No, PU Foam is very poorly UV resistant. If PU Foam is exposed to UV for a longer time it yellows and becomes very brittle. PU Foam is therefore always used behind building materials such as wooden paneling next to windows and doors.

Q. I read on my PU Foam canister B3 what does that tell me?

A. PU Foam is categized in fire classes each with their own reaction to fire.

B1- Difficult flammable / Fire retardant

B2- Normally flammable

B3- Flammable

Q. I know that my sealants comply with CE markings, I don’t see this on my PU Foam canister?

A. It is true that there is no CE marking on the canister (yet). It has been discussed about for some time, but to date it is not mandatory.

Q. What is Hand Held?

A. Hand Held means that the PU Foam canister must be activated by hand. That is, you turn the supplied applicator on the can, shake it well and activate it manually. There is also Gun Grade available, the applicator is replaced by a gun and the can is then activated by the mounted PU gun.

Q. Can I re-use a Hand Held canister?

A. That is precisely the limitation of a hand held quality. A hand Held is not re-usable after activation, so you will have to use the canister immediately. With a Gun Grade it’s possible to re-use because the can and gun remain under pressure and curing of the PU Foam can’tinitiate.

Q. I dropped some PU Foam on the floor how can I clean this?

A. You can easily clean your floor and remove fresh PU Foam with the Bostik PU Cleaner. As long as the PU Foam is fresh, the cleaner dissolves it easily.

Q. I noticed a water based PU Foam today on the shelf of my builders outlet, can I use this for the same applications as traditional PU Foams?

A. That's right, Bostik has also supplies an Acrylic foam. However, this quality does not concern a PU foam as the foam does not contain a polyurethane but an acrylic formulation. Acrylic foam can only be used indoors, such as interior doors, ceiling connection, wall finishing, etc. The product is immediately toolable and after drying can also be painted over with most paints, as you are used to with acrylic sealants. but understand, it is not a PU Foam and therefore cannot be compared with traditional PU Foams.

Surface Prep Products

Q. How clean does the subfloor have to be before I apply any adhesive?

Floor should have no stains, no oils, grease, dirt or any type of contaminants. For further questions, please contact your local Technical Representative for specific product recommendation.

Q. Can I pour the SLC over carpet, old vinyl, existing finished wood flooring, tile, etc.?

Bostik recommends Tile as an approved substrate as long as the current substrate is clean, well bonded and free of all contaminants. Other substrates are not recommended. For further questions, please contact your local Technical Representative for specific product recommendation.

Q. Do I have to add metal lath to the substrate prior on the SLC application?

Depends on substrate, Bostik required metal lath for single layer plywood. Concrete slabs in good conditions and properly prepared to received our products do not need metal lath. For further questions, please contact your local Technical Representative for specific product recommendation.

Q. Do I need to prime prior on applying the SLC?  Should it be diluted or prime as is, using the primer at full concentration?

Yes, primer is necessary and required in order to prevent future failures. For further questions, please contact your local Technical Representative for specific product recommendation.

Q. Do I have to prime between SLC applications?

Yes, you must apply a coat of primer between SLC Applications. For further questions, please contact your local Technical Representative for specific product recommendation.

Q. Can I mix the product to feel?

No, each product is designed based on product performances. Please refer to the specific product TDS for water demand and mixing instructions. For further questions, please contact your local Technical Representative for specific product recommendation.

Q. How long should I mix it? Does the product have a waiting time?

Always mix the material until is free of lump and it has reached a homogenous mix. No need to wait after mixed. Please refer to the specific product TDS for mixing instructions. For further questions, please contact your local Technical Representative for specific product recommendation.

Q. Can I add more water if it feels thick or I need to increase the flow?

No, each product is designed based on product performances. Please refer to the specific product TDS for water demand and mixing instructions. For further questions, please contact your local Technical Representative for specific product recommendation.

Q. Can I mix multiple bags at once?

Yes, no problem. Please refer to the product TDS for mixing recommendation methods approved by Bostik.

Q. Can I mix a partial bag?

No. It is crucial the correct amount of water is used in order to obtain the ideal performance of each product.

Q. I need a product that can seal and bond practically everything?

A. Bostik provides our end users a wide variety of general purpose products. Bostik advises you to acquire Bostik H750 SEAL’N’BOND PREMIUM a non-staining premium quality all-round hybrid sealant and adhesive.

Q. Can I apply a basic sealing & bonding product on natural stone? It doesn’t point this out on the cartridge?

A. Applying a standard sealing and bonding product on natural stone entails a risk of discoloration. This is caused by the plasticizers in the products, which migrate into the porous natural stone and discolor at the edges where the sealant meets the natural stone (looks like an oily character). there are special products available within the Bostik range that are specially suitable for this application.

Q. Is an general purpose product suitable on all substrates?

A. On a wide variety of surfacesgeneral purpose products are suitable except for PE, PP, PC, PMMA, PTFE, soft plastics, neoprene and bituminous substrates. if you are unsure, always check the Bostik technical data sheet.

Q. Do all general purpose products provide initial tack when bonding?

A. Initial tack products are highly specialized products specially designed to glue heavy objects to the wall or ceiling without any fixation. Bostik products only give initial tack if indicated on the packaging. In all other cases, we advise you to briefly support the object (an hour), after which a final bonding properties occur, after that the general purpose products will completely cure (2/3mm per 24Hrs).

Q. I bought a product from Bostik but it extrudes extremely heavily?

A. This may be because you have not cut the nozzle supplied with the cartridge. Small nozzle openings lead to heavy extrusion. If you cut the standard nozzle the product will extrude much better and without problems. For a problem free application of our products, we recommend a minimum opening of 6 mm at the nozzle.

Q. I have used the Bostik H550 for gluing skirting boards to the walls and seal them on top, can I paint it over?

A. Yes you can, our general purpose product Bostik H550 can be overpainted with water-based paints and 2C paints. When using solvent-based paint, a drying delay can occur so always test it.

Q. Which kind of paints can I us with the Bostik general purpose products?

A. All Bostik general purpose products are paintable with water-based paints and 2C paints, wall paints and lacquers no problem.

Q. Which general purpose products of Bostik can I apply for Bituminous roof applications?

A. Actually none, Bostik provides specialized roofing products for this.

Q. Can I fix a gutter with these GP products?

A. In principle, this could be possible, but Bostik also provides specialized products in our Roofing concept here.

Q. I have sealed my plastic windows now the glass is cracked?

A. This probably concerns a PMMA-PLEXIGLASS or POLYCARBONATE glass. If so, cracking of your glass is called stress cracking, stress cracking is the effect on the surface of plastic materials with a very low surface tension. Apply on this type of plastics only pure neutral silicone sealants without mineral plasticizers in our case Bostik S780 GLASS’N’SEAL PREMIUM.

Q. I have a crack in my Acrylic/Plexiglas this occurred a few weeks after I finished it with sealant.

A. PMMA-PLEXIGLASS or POLYCARBONATE glass generate very high movement coefficient, meaning  that if it concerns a large surface of glass sheets, they generate so much stretching power that the stiffer sealant cannot follow the PMMA-PLEXIGLASS or POLYCARBONATE glass which can eventually result in a crack.

Q. Can I use your glazing products for single and Insulation glass?

A. At Bostik we offer a wide variety of glazing product for any kind of glazing methods, single and monumental glazing and off course insulation glass.

Q. If I use your Hybrid glazing product, it sticks to my glazing tools.

A. Our hybrid product are very easy to apply and tool, however you need Bostik Finishing Soap to avoid your Hybrid to stick on your tooling materials.                               

Q. I have to finish monumental glass, does Bostik provide a glazing sealant for this?

A. Yes, Bostik certainly has, these are either the Bostik S950 GLASS 'N' SEAL PUTTY PREMIUM (technology Silicones) or the Bostik H950 GLASS 'N' SEAL PUTTY PREMIUM (technology Hybrids), where the Bostik S950 cannot be overpainted and the H950 can.

Q. I have a skylight, can I finish it with standard glazing sealant?

A. skylight probably concerns a PMMA-PLEXIGLASS or POLYCARBONATE glass. So, also here apply on this type of plastics only the Bostik S780 GLASS’N’SEAL PREMIUM.

Q. What joint dimension do I have to maintain when glazing a window?

A. Standard, window frames are delivered with glass with a joint dimension of approximately 4x4 millimeters, this can differ depending on the size of the glass plate profile, so the joint dimensions may be larger with large glazing systems. always use a PE cell tape to act as a backing rod, place it at the proper depth between 4-6 millimeters. Get well informed with your glass supplier what they recommend, this to rely on your possible warranty.

Q. Is it also possible to seal connection joints with my glazing sealant?

A. Yes you certainly can, glazing sealants are elastic high-quality sealants with excellent UV resistance. Be aware that silicone sealants cannot be overpainted, but Hybrid and polyurethane sealants can.

Q. Is it possible to partially renovate joints or do I have to completely clean and re-seal the window?

A. Yes you can, just remove all faulty sealants up to the healthy and intact sealant joints, then apply the new sealant joint. However we strongly advice to renovate the entire sealant while you are still working on the window frames. There is a chance that the current, older and intact sealant joint will also show irregularities on the short term. a little more effort but an optimal result.

Q. I now have a glazing joint and do not know what technology this is, can I use everything?

A. If you are not sure which kind of sealant has been used for your glazing system, we strongly recommend that you remove the entire sealant joint and provide it with a new glazing sealant. this will help you avoid compatibility issues at a later time.

Q. What is initial Tack?

A. A product with initial Tack provides you the opportunity to adhere a heavy object without any additional support to a surface (wall, ceiling etc.). Initial tack does not mean you have a higher strength after full curing, it may be that products without initial tack obtain an equivalent final stretch after curing. Initial tack solves a problem for you if it is not possible to glue certain items without any support.

Q. I have an Hybrid grab Does this product contains solvents?

A. None of our hybrid or acrylic grabs contain solvents.

Q. Does Bostik offers a water resistant Adhesive?

A. Bostik offers a Grabs & Adhesives portfolio to the markets with solutions for all general needs we encounter in our day to day job. Water resistance is one of them, Bostik produces a solvent free D4 water resistant extreme high strength polyurethane power adhesive for a wide range of applications.

Q. What types of technology does Bostik use to produce adhesives?

A Hybrid, solvent, water based and Polyurethane based adhesives.

Q. Is a Grab or adhesive universally applicable?

A No, depends on substrates, then application and finally the expected end result.

Q. When is a water-based adhesive recommended?

Often for indoor applications and when paintable is required, these adhesives are also solvent-free.

Q. When is a Hybrid glue recommended?

Often for outdoor applications, high and durable elasticity and a very wide adhesive spectrum. These products are also often used as 2 in 1 products (adhesion and sealing).

Q. When is a solvent-based adhesive recommended?

A These adhesives are generally very fast drying and curing, also when no elasticity is required and a solvent-based adhesive provides an excellent price/quality ratio.

Q. When is a polyurethane adhesive recommended?

A. Some polyurethane adhesives have a D4 waterproof certification and form a foaming character. Perfect for general interior construction and that of boat interiors, also available in a transparent version. often occurring in general construction and prefabricated constructions and also often occurring as 2 in 1 products

Hardwood Adhesives

Q. Do I need to get the entire old adhesive off the floor before I start applying the new adhesive?

Yes, slab must be contaminants free and well prepared before you can proceed with the Adhesive Installation. For further questions, please contact your local Technical Representative for specific product recommendation.

Q. Do you sell it in a smaller quantity?

Yes, Bostik offers some available in cartridges as well as in gallon buckets

Q.   How much adhesive do I need for my job, square foot coverage?

Based on flooring type and installation type, always refer to the product TDS. For further questions, please contact your local Technical Representative for specific product recommendation.

Q.   What is the difference between all the Bostik hardwood adhesives?

Varying moisture vapor protections, sound reduction, easy to trowel, no VOC, easy cleanup plus difference in polymer chemistries.For further questions, please contact your local Technical Representative for specific product recommendation.

Q.   Can I install over old glue-floor adhesive?

No, slab must be free of contaminants. For further questions, please contact your local Technical Representative for specific product recommendation.

Q.   Will these adhesives bond to various coatings on my concrete? (moisture barriers, sealers, cutback, etc)

Approved substrates are located on the technical data sheet. For further questions, please contact your local Technical Representative for specific product recommendation.

Q.   What size trowel do I use?

Recommended trowel sizes are located on the technical data sheet (TDS)specified upon type of wood and application. For further questions, please contact your local Technical Representative for specific product recommendation.

Q. What percentage of wood moisture can theframework have?

A. Framework must consist of preserved, dried back pinewood with a maximum wood moisture percentage of 18%. The wood moisture percentage can be measured by means of a wood moisture meter with the pins.

Q. What is the maximum center distance of the framework?

A. The center distances of the framework are specified by the panel manufacturer and can often be found in our Technical Data Sheet.

Q. Under what circumstances can I bond panels?

A. When bonding panels, we use a minimum temperature of 5°C and a maximum temperature of 30°C and the relative humidity also plays an important role in this. A dew point table is available for this. There should be no rain/precipitation.

Q. Do I have to pre-treat the framework and panels?

A. Yes, the system consists of 4 steps;

- Pretreatment of the framework, wood or aluminum (Black colored primer)

- Pretreatment of the adhesive side of the panel (Transparent primer)

- Place double-sided self-adhesive foam tape for fixation and spacer


Q. Can I apply the primer beforehand?

A. In principle, the best adhesion is obtained if the actual bonding of panels takes place within the set time frame. However, if the primer is applied beforehand, the applied primer coat must be kept clean and dry until bonding the panels.

Q. May I apply anextra primer layer over an already applied primer layer?

A. No, that is not allowed. If a fresh primer layer is placed over an already applied primer layer there is a very high chance of detachment.

Q. Can I also bond panels on horizontal framework?

A. Bonding panels on horizontal framework is not allowed, there must always be a continuous air cavity at the back of the panels of at least 20mm and ventilation openings at the bottom and top of the panel system of at least 50cm2/m1 or 100cm2/m1depending on the type of panel.In addition, the Bostik panel bonding system is 3 mm thick ultimately and a drain would be formed on horizontal details were water load can be collected and finally damage the adhesive and its durable properties.

Q. What time span do I have to  take into account when bonding a panel?

A. The open time of the adhesive BOSTIK H975 PANELTACK HM is 10 minutes.

Q. Do I have to provide extra mechanical support for the panels after adhesion?

The double-sided self-adhesive foam tape provides the 1stadhesion and gives the adhesive time to reach its final strength. Mechanical support is therefore not necessary.

Q. Can I also bond panels as ceiling panels?

A. Panels may be bonded as facade and ceiling panels, keep in mind that the framework are mounted perpendicular to the facade and that the center-to-center distance of the framework is always x 0.70 in relation to the center-to-center distance in the facade.

Q. What is Passive Fire Protection (PFP)?

A. Passive Fire Protection is built into the structure to provide stability and into walls and floors to separate the building into areas of manageable risk – compartments. These areas are designed to restrict the growth and spread of fire allowing occupants to escape and offering protection for firefighters. Such protection is either provided by the materials from which the building is constructedor is added to the building to enhance its fire resistance.

Q. What is the difference between active and passive fire protection?

A. Active Fire protection takes action in order to put out a fire. Passive Fire Protection will help prevent a fire from spreading or resist the initial ignition.

Q. What is the difference between reaction to fire and resistance to fire?

A. Reaction to fire evaluates specific materials contributing to fire, whereas resistance to fire assesses a system or products ability to resist the penetration through the system or products and prevent temperature rise between the exposed and unexposed sides in a fully developed fire situation. Reaction to fire is tested according to EN 13501-1 and fire resistance is tested to EN 13501-2. The Bostik Fire Protect Range focuses on fire resistance.

Q. Are our products approved for fire protection applications?

A. The products from the Bostik Fire Protect Range are tested to the European norms EN 1366-3 & EN 1366-4 and classified to EN 13501-2.

Q. Are the products from the Bostik Fire Protect Range also tested according to EN 13501-1 Reaction to Fire?

A. Yes, the majority of the products we have tested are determined in fire class B (little fuel and very low contribution to the fire, but they cause flashover).

Q. What solutions do Bostik offer regarding Fire Protection?

A. Bostik offers solutions for linear joint & gap seals and for penetration seals. Bostik offers different kind of products like  acrylic-, silicone- and hybrid based sealants, PU foam and products with intumescent properties like pipe collars & wraps and coating.

Q. What are service penetration seals?

A. Service penetration seals are passive fire protection systems designed to maintain the fire resistance of a building element or section (wall or floor) where services such as cables, cable trays or pipes pass through them.

Q. How do intumescent products work?

A. Intumescent products are designed to expand and fill any gaps in ire compartments to reinstate the compartment in the case of a fire. This type of fire protection doesn’t extinguish a fire but it contains it and prevent spreading of a fire.

Q. Can I use Fire Retardant PU Foam around pipes?

A. No, pipes and cables must be fire stopped with intumescent products that are tested for this specific application. Fire Retardant PU Foam is usually only used for sealing penetrations where there are no services going through. Bostik recommends the use of intumescent pipe collars or wraps to ensure the integrity of the wall and floor is maintained in a fire.

Q. Do the products from the Bostik Fire Protect range have acoustic properties?

A. Yes, the majority of the products have been tested for airborne sound insulation according to ISO 10140-2:2010.

Q. Although I have used a sanitary sealant, there is still mould. How is this possible?

A. Anti-mould additives are used to protect the sanitary sealants to prevent mould growth for a long period of time. However, if ventilation is poor or soap residue remains on the sealant joint for long periods of time, the anti-mould properties can be affected. Also cleaning the sealant with chloride based cleaners will negatively affect the protection evenly quicker. Once the mould protection is affected, Fungi can develop at a humidity of 65% and grow even faster at higher humidity. For more information please read the FactSheet FS014 Fungi resistance of sealants.

Q. I have sealed my bathtub with a premium silicones and it cracks?

A. You have probably sealed your bath as it was empty with your premium silicone sealant. Bostik always recommends that you let the bath fill up before sealing and only then apply the silicone sealant. This is because deformation always occurs when the bath is filled, this deformation between the bath and the wall creates an enormous stress on the silicone sealant with the result that the silicone sealant ruptures. So fill the bath, finish with silicone sealant, let it cure and drain again.

Q. I have bought a Silicone sealant and applied it in my toilet, now all joints are discoloring (yellowing)?

A. We suspect that you have used an neutral silicone and that you toilet doesn’t have a window. In that case neutral curing silicone sealant can discolor, this is caused by the lack of UV light exposure. Generally this phenomenon is occurring very graduate (over many years even) and is not being seen as a problem or complaint. If you want to avoid this in the future your solution is to buy a acetoxy (sour/acid-smelling) silicone to avoid yellowing, Acetoxy silicone are not sensitive to discoloring in areas where there is lack of UV light exposure.

Q. What kind of tools or additional products does Bostik recommend to apply and finish a silicone joint correctly?

A. Bostik recommends using a tooling agent and spatula (wood or plastic). The Bostik tooling agent ensures that the silicone sealant does not stick to the finishing spatulas or adjacent surfaces and ensures complete compatibility with the silicone sealant. That being said, when you apply the silicone sealant make sure it is applied full and completely filled your joint. if the Bostik finishing agent accidentally gets between the silicone sealant and the substrate, loss of adhesion will take place here.

Q. Do I need always to tape the joint for applying a silicone?

A. If you are a professional application specialist, you can probably apply a sealant joint almost perfectly without tape. If you are not sure of your application properties or if it is really necessary that other places should not be affected by the sealant, we recommend that you tape off the joint(make sure the tape is only used shortly) and immediately apply the sealant and finishing with your spatula, remove the tape and smoothen (very carefully) the sealant joint once more for the best possible result.

Q. In the store many different sanitary sealants have been set up in the store, how do I make the right choice?

A.That depends on your application and desired end result. Do you need to seal a drainage or finish a window frame in your bathroom? Is paintability an issue? Unfortunately, an unambiguous answer is not available. Visit us at or participate in one of our training courses at the Bostik academy to make the right choice.

Q. What is the difference between a neutral or acetoxy silicone?

A. You can recognize an acetoxy silicone by the acidic odor that is shortly released when extruding the cartridge neutral silicones have very minimal odor sensation.

  • Acetoxy silicone, do not discolouring in dark places but have a limited adhesion spectrum (glass, painted wood, enamel and ceramics).
  • Neutral silicone, have excellent adhesion to wide range substrates, are not corrosive but can discolour in dark places because of lack of UV exposure.
Q. My Hybrid sealant has a sanitary CE mark, yet I am having problems with my shower drain, how is that possible?

A. Hybrid products can be tested and certified with the highest possible CE marking on sanitary (EN 15651-3: S XS1). However, hybrid sealants are not suitable for continuous or long-term water exposure. The CE marking only says something about the growth of bacteria culture on the sealants, not about its applicability. Anti-fungal silicones are the best solution for this application.

Q. What does EN15651-3:S XS1 means that’s highlighted on my cartridge?

A.EN15651-3:S XS1 is a so-called CE marking for sanitary use this product can be used in a sanitary environment and is tested via European harmonized test methods by independent test institutes. As from July 2014 it’s mandatory within the EU to certify all sealants with a CE marking, adhesives are (for now) excluded from a CE certification. EN15651-3:S XS1 is the best possible CE marking on the markets to achieve.


Soft Flooring

Q. Can I use a hardwood-flooring adhesive to adhere a vinyl floor covering?

No, for further questions, please contact your local Technical Representative for specific product recommendation.

Q. Does the Soft Flooring Adhesive provide a moisture vapor barrier?

No, Bostik has specific products developed for moisture and vapor barriers. For further questions, please contact your local Technical Representative for specific product recommendation.

Q. Can I use this over an existing vinyl floor?

Yes, based on the industry association, you can only bond to a maximum of 2 layers together as long as it is kept in good conditions, well bonded, clean and free of any divots and other contaminants. For further questions, please contact your local Technical Representative for specific product recommendation.

Q. Is this a wet lay installation or is there a flash time?

Flash time is required. For further questions, please contact your local Technical Representative for specific product recommendation.

Q. What is the RH% moisture rating of this adhesive?

Relative Humidity (RH)% readings are derived from the ASTM and European norms. These reading will vary depending on the adhesive; they range from 85-95% RH. (With some exceptions, we will allow a 99% RH rating). For further questions, please contact your local Technical Representative for specific product recommendation.

Q. What type of substrate preparation is needed prior on applying the adhesive?

Follow the ASTM or current norm standard for floor preparation; free of dust and paint, markings oil, curing or release agents, sealers or existing adhesives. For further questions, please contact your local Technical Representative for specific product recommendation.

Q. What trowel size is needed?

Trowel sizes and coverages are located in the technical data sheet. For further questions, please contact your local Technical Representative for specific product recommendation.

Q. What is the working time of the adhesive?

The dry lay method is the most common installation method used for a PSA adhesive. Once the adhesive is dry to the touch the working time is the amount of time the installer has to lay the flooring into the adhesive before it becomes less effective in bonding and tackiness. For further questions, please contact your local Technical Representative for specific product recommendation.

Tile Products

Q. How long  do Tile Adhesive Mortars need to cure before I grout?

The time varies based on the type of tile, where it’s being used, type of substrate and type of mortar being used. Please refer to the TDS for specific product recommendation and specification.

Q. How much water is needed, how do I mix less than a full bag?

Please refer to the mixing instructions on bags and TDS. For areas where you will be using less than full bag mix, weigh powder and measure water based on the bags or TDS instructions. For further questions, please contact your local Technical Representative for specific product recommendation.

Q. How do I select the best Tile Adhesive Mortarfor my job?

The correct Tile Adhesive is selected based on the type of tile, where it’s being used and type of substrate.For further questions, please contact your local Technical Representative for specific product recommendation.

Q. Should it be modified or non-modified?

Recommended based upon the type of substrate and tile. For further questions, please contact your local Technical Representative for specific product recommendation.

Q. Will the mortar bond to various substrates?

Refer to the TDS for specific approved substrates. For further questions, please contact your local Technical Representative for specific product recommendation.

Q. What size of trowel should I use?

Trowel size will depend on the tile size and where is being installed. Please refer to the product TDS for specific recommendations.



Q. How can I remove haze?

Please refer to our Bostik haze removal line. For further questions, please contact your local Technical Representative for specific product recommendation.

Q. Do I need to seal the Tile-Grout? What can I use?

Any sealer at local home building supply store will work for Cement Base Tile Grouts. Urethane Grouts must use awater-based sealer. For further questions, please contact your local Technical Representative for specific product recommendation.

Q. Why are there color variations in my Tile Grouts?  

Color variations are due to the amount of water added in the initial mix, too much water used to wipe down the tile/too soon after grouting, etc. For further questions, please contact your local Technical Representative for specific product recommendation.