Over the past few years, my firm Stone Forensics has been called into to investigate several problems with both stone and quartz materials. The following are some examples of these problems.
Case #1. A customer had a tropical green granite bar installed on their pool deck. Shortly after installation, the countertop started to get darker and darker.
Case #2. A granite top was installed next to a barbeque pit. Several months after it was installed It developed a crack. The fabricator replaced the piece and it again cracked after being installed. The fabricator again replaces the granite but this time with a different type of granite. It also cracked.
Case #3. A quartz table was fabricated and placed on an outdoor pool deck. After one summer the table began to develop spider cracks all over the top surface.
Case #4. An outdoor granite bar started having a sticky residue appearing on the surface. It could be removed with acetone but it kept coming back.
Case #5. A red quartz countertop was installed on an outside bar and within three months it turned pink UV light and the type of resins used in both granite and quartz surfaces.
Case #6. A fabricator profiles a piece of stone, polishes it, and notes that the profile is lighter or a different color than the top surface.
All of these failures are the result of exposure to UV light.
How does UV light work
The following is a definition found on Wikipedia.
Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than x-rays, in the range 10 nmto 400 nm, and energies from 3eV to 124 eV. It is so named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the color violet.
UV light is found in sunlight and is emitted by electric arcs and specialized lights such as black lights. As an ionizing radiation, it can cause chemical reactions, and causes many substances to glow or fluoresce. Most people are aware of the effects of UV through the painful condition of sunburn, but the UV spectrum has many other effects, both beneficial and damaging, on human health.
Now what this means is that UV light is nasty and can break down almost any material. If you ever place a PVC pipe in the backyard over the summer and then take a hammer and tap it, you would find it is brittle. Another example is how your car’s paint will fade over time.
UV light is very destructive to almost all polymers. The process is known as polymer degradation. This is why many plastics have UV absorbers which will inhibit UV Degradation,
Well if you know anything about quartz surfaces and granite resining you will know that they are made with and impregnated with polymers such as polyesters and epoxies. Many of these polymers do not contain UV absorbers and for this reason, the UV light starts to degrade the polymers leading to cracking, fading, and complete breakdown. I have even seen UV degradation occur indoors where a countertop is exposed to sunlight. Glass will protect and reduce some UV rays but not all. For more information on the resining process see my blog at www.thestonedude.blogspot.com.
So, how do you prevent these failures, and more importantly, can they be repaired:
First, let’s take a look at prevention. If a customer wants an outdoor cooktop, bar, or whatever you must take a close look at the material that is to be used. Ask the quartz surface manufacturer if their material can be used outdoors. Many will say no. But as technology develops you may find improvements in resin technology that might overcome or at least hasten the effects of UV degradation.
If you are using granite outdoors ask if the stone is resined. You can request a non-resined granite. If you have doubts there is a test kit available that can tell you if it’s resined or not. You can find this kit at www.stonecarecentral.com under specialty kits.
I would advise your customer to keep the countertop coved with a breathable fabric when not in use. This will shade it from the UV rays. I have also had tinted plastic glass cut to size and placed on the tops when not in use. I haven’t tried applying sunscreen to it and would not recommend it LOL.
Keep in mind that natural stone will also fade naturally but it generally takes years for fading to occur.
Always discuss this with your customer and you will prevent that late afternoon phone call that will ruin your weekend. I find it helpful to have them sign a waiver or disclaimer.
Frederick M Hueston is the founder of Stone Forensics and has over 30 years of experience in the stone business. He has written over 30 books and hundreds of articles. He currently is technical director for stone and tile Pros (stoneandtilepros.com) and hosts a weekly radio show, The Stone and Tile Show at www.blogtalkradio.com.drfred.