Efflorescence and Volatile Organic Compounds (VOC) - & BYNE?S DISEASE A look at how VOC?s can contribute to efflorescence and the Aqua Mix products that can help prevent these problems.
Over the last year I received several questions directed towards efflorescence in marble and limestone. More importantly in several of these installations the efflorescence damaged the polished surface and repeated the damage after subsequent repair. There is no doubt that it can cause this damage. We are all familiar with efflorescence (soluble salts) and how it occurs. It is basically a chemical reaction between soluble salt (present in the stone and or setting materials and substrate) and oxygenated water. It also requires higher temperatures.? The salt crystals expand and contact as they wet and then solidify creating pressure in the stone similar to freeze thaw damage. The weaker stylolite seams (veins) offer both entry points for water to start the chemical reaction as well as reservoirs to hold the crystalline salt. The damage will continue as long as there is a source of soluble salt, explaining why efflorescence and it?s associated damage can return after cleaning. However in some cases the source of the salt and catalyst are not what they may appear to be. To understand and prevent this type of damage you need to understand ALL of the possible sources and causes of efflorescence. The least understood of these are Volatile Organic Compounds (VOC?s)
In 1899 a gentleman by the name of Byne tested and concluded that a white growth (efflorescence) on calcareous materials was due to a reaction between butyric acid and the surface of his specimen white shells. He believed the source of the acid was the timber used to enclose the shells. More recent investigations have further concluded that salt can form from reactions between calcareous materials, water and fumes such as acetic acid, formic acid and formaldehyde. These are all found in timber such as chip-board (from the lignin-based adhesive) and MDF. Therefore the link between efflorescence and VOC?s (Volatile Organic Compounds) has been scientifically established. The mechanism is referred to as Byne?s disease.
The importance of this finding is totally overlooked in the stone industry when looking for the sources and solutions for efflorescence. Therefore when investigating an efflorescence problem you need to look at the traditional sources as well as possible sources of VOC?s. Hence check out the following. ?
1.????? The stone and cement. Obviously some stone?s have naturally occurring soluble salts as do sand and cement. Some stone, especially those associated with oil deposits may also give off some VOC?S. With water being the catalyst sealing the stone on all six sides is the only preventative measure. For the concrete? - use washed sand and where possible use a waterproof membrane over a concrete substrate to divorce the stone from the cement.
2.????? Adhesive. Some adhesives contain VOC?s that can create the problem. Install with safe VOC compliant adhesives.??
3.????? Timber. Byne?s disease and the link of VOC?s as a component of the efflorescence reaction establish timber as a possible problem. Some plywoods and chip-boards (MDF) can contribute by their VOC?s creating salt such as calcium acetate hydrates. The solution is to use timber substrates that either have no VOC?s or to isolate them with waterproof membranes. A sheet membrane is best as it has low vapour transmission thus reducing quantity of VOC?s that may move through a high vapour transmission membrane. This should also include any timber furniture or fittings that are exposed to the stone as these will give off potentially damaging VOC?s.?
4.????? Acids. Acid used to clean or hone a stone (especially acetic based acids) can become reactivated if not properly neutralised. The resulting VOC emitted can spark efflorescence; the solution is to not use acids. However if an acid is required then use less aggressive acids such as phosphoric and most importantly rinse and neutralise correctly.
5.????? Water. Controlling and preventing moisture (water and vapour) from getting to the stone, substrate or source of VOC is perhaps the most important precaution. Efflorescence simply cannot form if there is no water. Take the water away and all possible sources of salt cannot become soluble. Therefore use waterproof membranes to keep substrates as well as possible sources of VOC?s dry. Use latex modified cements and grouts to reduce the amount of water needed to hydrate. Use sealers to reduce the amount of water that travels into the stone and installation system.
In summary the link between VOC?s and efflorescence is well documented. Their contribution is however not well recognised in our industry. Do not overlook their effect when investigating an efflorescence problem. A complete analysis and solution must involve a total installation system in which our Aqua Mix sealers, safe neutral cleaners and mild phosphoric acid play a major role.