by Jay Watts, Technical Director, American Formulating & Manufacturing (AFM)
Wherever possible and appropriate, we incorporate surface sealing properties into AFM Safecoat products such as paints and clear finishes. Many chemically sensitive individuals have successfully controlled off-gassing materials using Safecoat, to the extent that they can tolerate environments that were intolerable before.
Every indoor air quality problem, and every surface, is different, so there are no guarantees. But follow these basic rules and critical steps for the best chance of success:
It's crucial to understand exactly what it is on the surface that's causing the problem. Is it a finish, is it in a material under a finish (such as drywall
under paint) or is it something 'under' the surface (an example of subsurface
contamination might be smelly carpet padding under carpet).
The closer the sealer can get to the off-gassing material, the more effective it's likely to be. Sealing works best when dealing with chemical emissions. Off-gassing from organic and related sources, such as food, pet odors, mold and mildew contamination, cigarette smoke and fragrances typically can not be sealed.
Proper surface preparation is absolutely required for good results. Tips are on our product data sheets and of course on the cans, but ultimately responsibility for understanding the surface and what needs to be done to make it ready to accept the sealer lies with the installer. Here are a few general tips for preparing your surface:
Any surface sheen needs to be de-glossed. Mechanical de-glossing is the best. There are some chemical de-glossers such as TSP, but these can leave unwanted residue on the surface that inhibit sealer adhesion, and so are discouraged.
All patching and repairs should be done and allowed ample time to cure. Consult the manufacturers of these products for appropriate cure times.
Always make sure your surfaces are clean, dry and dust free.
Environmental conditions during and following application are very important. Water-based products dry and cure more effectively when surface and air temperature are in the mid 70's with humidity at 50% or lower. If colder or more humid conditions are present, allow more time for drying and between coats.
To promote curing and a stronger, faster seal, move air over the coated surface constantly. Simple ventilation is necessary but rarely sufficient. Use of household or, if available, commercial fans will promote evaporation of all moisture in the coating, which is ultimately necessary for creating a strong film on the surface.
Application techniques affect drying/curing times. Thicker coats dry more slowly than thinner ones.
Multiple thin coats are always better than fewer thick ones.
The ultimate results will depend upon the severity of the contamination, methods of application, number of coats and environmental conditions affecting the installation. Many times a multiple coat application (3+ coats) will be necessary to solve a significant off-gassing problem. There are no hard and fast rules on how many coats will be necessary, as each indoor air quality problem tends to be unique and as such to require individualized handling of the problem. The following chart gives some basic reference points with regard to the effect of various AFM Safecoat products upon formaldehyde off-gassing from plywood.
Sample Primer Coat Finish Coat Formaldehyde Evaporation mg. Per liter
VOC Semi-Gloss . .03
VOC Semi-Gloss 0
VOC Semi-Gloss .04
BP Gloss Polyureseal BP Gloss .02
Finally, the biggest qualifier to success is personal tolerance to the offending chemistry and the products used to mitigate the pollution. Accordingly, AFM strongly recommends that all users and applicators, especially those sensitive to chemicals, test products for personal tolerance before using. Test samples of all AFM Safecoat products are available for this purpose from Green Building Supply at 800.405.0222.