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Do I need to use a primer before sealing?

It is recommended in almost all situations, especially when you are dealing with porous substrates. Refer to the sealant TDS for more details.

What is the correct dimension of the joint sealant?

The correct dimension of a joint sealant until 10mm is 1 on 1 (e.g. 5mm in width and 5mm in depth). If your joint width is broader than 10mm you can easily calculate the right dept by using the following calculation;

Correct depth = 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. A durable joint sealant is depending on the movement of the adjacent building elements and the use of a correct backer rod.

When is a backing rod recommended? 

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.

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

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 using Bostik 5CLM when sealing marble and granite joints *(Stain testing must be carried out first before use on any project)

How should I store caulkable adhesives? 

In general, these products should be stored between the range of 5oC to 25oC

It is also important that moisture does not get into the packaging as it will start the curing process and the product will become hard and unusable. 

Can I paint silicone sealants?

No, paint does not adhere to a silicone sealant. If you need to paint the sealant after application, we recommend Seal 'N' Flex® Facade H725 in façade joints. For more information please read the TDS.

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

During curing acrylic joints will show shrinkage because of evaporation of water, which is part of all acrylic formulations. If you overpaint the acrylic joint too soon prior to cure, the paint isn’t flexible enough to withstand this deformation, causing cracking of the paint. If you look closely, it is the paint that has cracked, not the sealant. Follow TDS instructions regarding paintability of products.

I just bought an existing house and I have all kinds of cracks and holes in my wall and ceiling.

Depending on size of the cracks and substrate, we recommend Bostik Expanda Foam and Bostik Gap Seal. Refer to TDS for more details.

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

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 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.

Are all paints compatible with Bostik acrylics?

It is impossible for us to test all paints and paint qualities on our acrylic products. Always carry out pre-test to be sure.

Can I use an acrylic outside?

We recommend using a PU or hybrid sealant for exterior areas. Check out the Seal 'N' Flex® range for more details.

Can I use an acrylic sealant for glazing?

No, unfortunately that is not possible. Acrylic sealants do not have the same movement capability as a glazing sealant (elastic sealant).

How elastic or flexible is an acrylic?

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 constant 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.

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

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

I have a can of PU Foam, but when activated the PU Foam doesn’t come out?

If the can of PU Foam was stored in a lying position, solids in the can 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.

Can I paint over PU Foam?

Yes painting of PU Foam is possible.

What is Hand Held?

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.

Can I re-use a Hand Held canister?

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; the can and gun remain under pressure and curing of the PU Foam can’t initiate.

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

You can easily clean your floor and remove fresh PU Foam with the Bostik Handy Wipes. Cured PU foam will need to be removed mechanically.

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. 

Can I pour the SLC (self-levelling compound) over carpet, old vinyl, existing finished wood flooring, tile, etc?

Tile is a suitable substrate as long as it is clean, well bonded, and free of all contaminants. Other substrates are not recommended. 

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

Yes, primer is necessary and required in order to prevent future failures. Refer to the relevant TDS for primer recommendations.

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. 

Can I mix multiple bags at once?

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

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.

How do I pour levelling compounds to 100mm thick?

Bostik manufacture a number of cementitious floor levelers that are recommended for applications up to 75mm in depth at any one time. Should greater depths be required, it means that multiple applications of the product are required to achieve the required depth.

Our range of Ultra Level SLC can be bulked out to reach 100mm, with specific advice listed in the relevant TDS.

This addition will not have any detrimental effect on the application properties, or the final properties of the products. With this addition, the products may then be applied at thicknesses up to a maximum of 100mm in one application.

How do I store powders? 

These products must be stored dry – any moisture that comes into contact with a powder adhesive will begin the curing process. If moisture has gotten into the packaging, either from the storage or transport conditions, the powder forms lumps or rocks that cannot be re-mixed into the glue.

Can I use your glazing products for single and insulation glass?

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

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

Standard, window frames are delivered with glass with a joint dimension of approximately 4x4mm. 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 4-6mm.

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

Yes. 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.

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

You can partially renovate joints; just remove all faulty sealants up to the healthy and intact sealant joints, then apply the new sealant joint. However we strongly recommend renovating 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.

I have a glazing joint and do not know what technology it is, can I use everything?

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.

What types of technology does Bostik offer in adhesives?

We offer hybrid, solvent, water-based and polyurethane based adhesives.

When is a water-based adhesive recommended?

Often for indoor applications and when paintable is required.

When is a hybrid glue recommended?

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).

When is a solvent-based adhesive recommended?

Solvent-based adhesives are generally very fast drying and curing, and can be used when no elasticity is required. They also provide an excellent price/quality ratio.

When is a polyurethane adhesive recommended?

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.

Do hybrid grabs contain solvents?

No Bostik hybrid or acrylic grab contain solvents. 

What is initial tack?

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 doesn't 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.

Do I need to remove 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.

Do you sell the Ultraset® Flooring range of adhesives in a smaller quantity?

Yes, Bostik offers some available in cartridges as well as pails

What is the difference between all the Bostik Ultraset® adhesives?

Varying moisture vapor protections, sound reduction, easy to trowel, no VOC, easy cleanup plus difference in polymer chemistries.

What size trowel do I use?

A 3-4mm trowel is recommended for Ultraset® SF and Ultraset® HP

A 6mm trowel is recommended for Ultraset® 2 in 1 and Ultraset® 3 in 1

How do I adhere acoustic mat for under timber floor applications? 

Acoustic mat is only required when using Ultraset® SF & HP. 

The primary substrate usually consists of concrete, screed, or compressed fibre cement sheet. Preparation should be undertaken to prepare the floor to the requirements of the adhesive chosen as laid out in the Technical Data Sheet. 

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

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.

I have sealed my bathtub with a premium silicone but it still cracks.

You may have sealed your bath when 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. Deformation always occurs when the bath is filled, and this deformation between the bath and the wall creates enormous stress on the silicone sealant, resulting in silicone sealant ruptures. So fill the bath, finish with silicone sealant, let it cure, and drain again.

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

You may have used a neutral silicone in an area with poor ventilation. Neutral curing silicone sealant can discolor, due to the lack of UV light exposure. Generally, this phenomenon occurs very gradually (over many years even). To avoid this, ensure you use an acetoxy (acetic cure) silicone. Acetoxy silicones are not sensitive to discoloring in areas where there is lack of UV light exposure.

What's the difference between neutral and acetoxy silicones? 

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

  • Acetoxy silicone doesn't discolour in dark places, but has a limited adhesion spectrum (glass, painted wood, enamel and ceramics).
  • Neutral silicone has excellent adhesion to wide range substrates and are not corrosive, but can discolour in dark places because of lack of UV exposure.




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

No, Bostik Resilient Adhesives are recommended for vinyl floor covering. For further questions and to get an specific product recommendation, please contact your local Technical Representative for specific product recommendation.

Can I use Bostik Resilient Adhesives 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.

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

Flash time is required. 

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).

How do I apply a PSA adhesive?

The dry lay method is the most common installation method used for a PSA adhesive. Once the adhesive is dry to touch, soft floor coverings can be installed.

How do I tile to HardieTex™ blue board?

The answer here is simple – do not tile to HardieTex™ blue board or any other version of blue board.

Blue board as a substrate is made for use under render or textured coatings. If blue board is installed as a substrate it is in your best interest to refuse the work as neither Bostik nor the blue board manufacturer will be able to provide support in the case of system failure.

How do I tile to particleboard?

The best method to employ is to install a fibre cement sheet tile underlay over the particleboard prior to tiling.

How do I tile to timber flooring?

Before tiling over timber, it is advisable to contact the timber manufacturer for advice regarding the required preparation. Not all timbers can have tiles bonded directly to them. The density and oil content of the timber will have a bearing on how successful the installation would be. If in doubt, it is best to install a suitable ceramic tile underlay over the timber prior to tiling.


Can I use a roller to apply Dampfix® 1K?​

Dampfix® 1K can be applied by brush, roller, trowel, or spray equipment. The mixing ratio can be adjusted in order to obtain the consistency and workability desired for the intended application.​​

Does Bostik have a bond breaker tape for junctions, joints, and corners compatible with Dampfix® 1K?​

Dampfix® Instant Seal is a self-adhesive waterproofing tape compatible with our Dampfix® range. This 100mm wide tape can be used as a bond breaker in joint, junctions and corners.​

Do I need to prime when using Dampfix® 1K​

Dampfix® 1K can be applied to dampen porous substrates (no free water); priming is not required if the substrate is in sound condition. We recommend the use of a primer to avoid pinholes and other issues.

Is there an alternative product to Dampfix® Platinum in the market?​

This is a brand new product in the waterproofing market that caters for most waterproofing application areas, from internal wet areas to planter boxes to roofs and more. ​It eliminates the need to buy 5 products for one job. There is no direct equivalent product in Australia

Can Dampfix® Platinum withstand positive and negative hydrostatic pressure? ​

Dampfix® Platinum is not designed to withstand a negative head of pressure. Depending on the application, we recommend using Ultra Moisture Seal as a primer first, or using our alternative waterproofing product, Dampfix® 1K.​