What’s the Deal with Yellow Coatings?
If you’ve ever coated an oil- or asphalt-based roof (such as modified bitumen or tar) and seen it begin to yellow afterwards, you may be asking yourself “Why Did My Silicone Roof Coating Turn Yellow?” This blog looks into the science behind this question and identifies how Progressive Materials can prevent the yellowing from occurring.
Oil-/Asphalt-Based Roof’s Problem
The main issue with oil/asphalt-based roofs is that these substrates have heavy oils in them. These oils will always leach out of the oil/asphalt and work their way to the surface. Although this leaching will not affect the adhesion of PM Silicone in any way, it can create a yellowing effect to the coating. You could see this on newer EPDM roofs as well – typically 5 years of age or younger. Fortunately, PM has a solution to mitigate yellowing on these roof types.
This is what yellowing can look like if silicone is put down without a primer on mod bit. PM’s primers prevent this yellowing from taking place.
PM’s P-160 Asphalt Bleed-Block Primer and P-110 EPDM Bleed-Block Primer prevent this discoloration if applied before the Silicone Top Coat. These primers block these oils from leaching, or bleeding, into the silicone will prevent the yellowing altogether. Our bleed-block primers and intended to be sprayed, rolled, or brushed on with ease. Once applied and dry, the Silicone Top Coat can be sprayed or rolled onto the roof. The primer will offer protection from yellowing, and the roof will be seamless and waterproof with multiple other benefits.
Oil- and asphalt-based substrates are almost always great candidates for a silicone roof restoration. PM Silicone adheres great to these substrates and can help restore them and keep them watertight. If, however, the roof is in a high visibility area or the building owners wants to retain their bright white coating, this oil bleed through can stain the coating. Thankfully, our full line of silicone products, primers, and accessories has everything you need to restore these roofs and keep them beautiful for decades!
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