WHAT TYPES OF IMPREGNATORS ARE THERE?
Impregnators can be broken down into several categories. They can be water- or solvent-based. Most impregnators also contain one of two main ingredients: silicon derivatives or fluoro alphatics. In general, the silicone types repel water and the fluoro types repel both water and oil. Many companies are going to strictly water-based formulas because of the fact that they are safer to use, have little odor and are better for the environment.
ARE SEALERS SAFE FOR FOOD HANDLING AREAS?
This will all depend on the manufacturer. Generally, once the impregnator has dried and cured it should be safe for most food handling situations. However, to be sure, check with the product’s manufacturer.
WHAT PROBLEMS HAVE YOU COME ACROSS WITH IMPREGNATORS?
The problems I have seen to date are few and almost always caused by misapplication of the product. If the impregnator is left on the surface of the stone and the excess is not removed, it can cause the stone to be sticky, making removal difficult.
Recently, I have seen some solvent-based impregnators reacting to resinated slabs, causing clouding or discoloration. Another problem is applying an impregnator to a wet stone. If the stone is wet, the impregnators will not penetrate and therefore will not perform as expected, but overall, most impregnators are trouble-free.
HOW OFTEN MUST AN IMPREGNATOR BE APPLIED?
This will also depend on the type and use of the stone. I generally recommend they be applied about once per year. More frequent applications may be necessary for commercial applications.
DOES ALL STONE NEED TO BE SEALED?
This is an ongoing debate in the industry. There are those who say that all stone needs to be sealed and others who say that only some very porous stones need sealing. The best way to find out is to perform a simple absorbency test as follows: Place about a teaspoon of water on the stone surface and allow it to sit for one to two minutes. If the stone becomes dark under the water, which indicates that it is absorbent, then the stone will need to be sealed.
ARE SEALERS AND IMPREGNATORS UV-RESISTANT?
Again, this will depend on the type of stone. In general, because they work below the surface, most will be UV-resistant. Remember that UV light is very powerful and will eventually have an effect on any sealer or impregnator. Most topical sealers, however, are not UV-resistant and will discolor over time.
The above information is based on current knowledge, but one must be aware that the chemistry of impregnators and sealers can and will change. My best advice is to keep up with current trends and ask plenty of questions when looking into any new product.
About the author: Frederick M. Hueston is a worldwide expert on stone installation, failures, fabrication and restoration. He is the founder of the National Training Center for Stone & Masonry Trades (ntc-stone.com) and Stone University (stoneuniversity.org). He can be reached at Fhueston@aol.com.