Before going further in discussing an acoustical coating, it would be best to first describe such a product and its typical application.
The greatest demand for an acoustical coating is to refinish the surface of a product that has an acoustical property (it absorbs sound) and the intent is to apply this new finish without damaging the sound absorbing quality. Again, the greatest demand is for ceilings … hence the term “Acoustical Ceiling Coating” is a common term.
Whatever the case, a distinction should be made between a conventional paint product and an acoustical coating. Further, there should be a concern that if the wrong product is applied to an acoustical surface, it cannot be removed easily and the cost for such a mistake could be considerable. The intent of this article is to provide some insight as to what an acoustical coating is capable of doing and some suggestions on how to go about identifying one with a degree of confidence before it is applied.
What the Acoustical Coating is Able to Do
First, look at the surface of an acoustical material such as an acoustical ceiling tile, or acoustical plaster. Notice that there are little holes or crevices throughout, or often course irregular surface textures. Below the surface there is a softer spongier material that is designed to absorb sound.
There is only one way that the sound waves can pass through the outer surface and be absorbed by the spongy inner material and that is through the holes on the surface. Therefore, any coating that is applied to the surface must be formulated to leave those holes open and not plug them up with paint pigment. The acoustical coating, therefore, is a “non-bridging” material. In other words, the molecules of the product will not link up to span or “bridge” a gap or other open spaces.
How to Select an Acoustical Coating
As stated, once the material is on the surface, it is too late to learn that it is not a true acoustical coating. The research must be done before the purchase, not after it. A label or brochure, produced by the neighborhood printing company, may contain many claims but that in of itself should not satisfy the more discriminating buyer. After all, they will print whatever copy is given to them.
Legitimate acoustical coating manufacturers have their products tested by independent laboratories in order to (1) ensure, from a product development perspective, that the product performs as intended, and (2) support the claims they intend to make in their promotional literature. These laboratories use the appropriate ASTM Test and since they are independent, they produce test data that are impartial. UL and FM Approvals are examples of accredited laboratories in the United States that are highly respected for their independent testing procedures.
If the product manufacturer can produce reasonably current test data that shows that the application of their product has no negative affect on the sound absorbing quality of the surface material, then it is safe to consider its purchase. One must be sure that the testing has been repeated recently, as formulas can be occasionally modified, particularly during harder economic times, when the cost of quality raw materials is on the rise.
Another test that is commonly run on an acoustical coating is a fire test. In other words, if there were a fire, how fast would the flame spread with this coating material on the surface? And further, in the burning of that surface material, how much smoke would be developed? Since people die more of smoke inhalation than heat, this is an essential consideration in selecting a product.
The better the acoustical coating, the slower flame spreads and the less smoke is developed. That is why most quality acoustical coatings carry a Class-A fire retardant rating.
One last word on independent laboratory testing has to do with product approvals. Independent laboratories offer a product approval classification. If a product is “approved” by a laboratory, it means more than they have tested the material. It means that they make periodic visits to the manufacturing facility in order to determine that the formulation remains consistent and that quality control procedures are in place and used.
Therefore, prior to selecting a product to be applied to an acoustical surface, check for independent laboratory testing and if possible, an “approved” product.