It's generally assumed to be UV light that causes yellowing. That would mean sunlight but also some types of artificial light. Nicotine can also play a part although it should clean off.

Having seen some drums that are very evenly yellowed despite not ever being evenly exposed to sunlight I suspect there may be other causes that can cause yellowing. Either a chemical reaction within certain batches of the wrap or perhaps due to excess heat such as a set stored in an attic for decades. I'm unsure but when the underside of a bass drum that never faces the sun fades exactly the same as the top of the drum it seems that UV as the sole cause is less likely.

Keeping them out of the sun seems a good policy no matter what.

Also, is it not true that gigging in tobacco smoke filled rooms can cause yellowing?

I think that I remember reading that the acetate wraps of yesteryear are prone to discolor from aging. Perhaps that factor plus the interaction from the old-fashioned adhesives for laminating the wrap to the shell will lead to the discoloration.

It's caused by reactions among adhesive, wrap material, type of colorant used and environment (UV light, smoke, temperature, etc.). Even the type of wood under the wrap would sometimes come through as the wrap colors faded...Too many variables to be able to say exactly what causes each and every example...

Green sparkle was another example that reacted very quickly to UV light and often faded unevenly. That's why you don't see too many green sparkle kits in mint shape.

I've got an old "Sherwood" snare drum that was made when Conn owned the Ludwig name...drums made at the old Leedy/Ludwig factory...1953-ish if I recall correctly...perfectly butter yellow WMP -which I find MUCH more beautiful than the bright white.

I agree with the buttery yellowed WMP as looking very classy.

Thanks guys, for those responses. Understood and appreciated. I will brighten up my practice room (to try to stop the mildew issue), warm it up a bit...and use a foil "survival blanket" to cover the WMP kit when I'm not sitting at it. Try to "cover all bases!"

Future yellowing? Beyond my control, but I agree that a mild "buttery" yellowed WMP looks good! In fact, to my eyes, it looks better than a brand-new bright WMP kit that hurts the eyes. Whatever floats your boat.

O-Lugs, there was a green sparkle Ludwig kit on Reverb a few days ago and the fading was enormous (and uneven) between the 3 drums. They looked really bad.

Regards, MB

The buttery yellow pearl looks very nice. The down side is when you need or want to add on a drum because finding one that matches becomes very problematic.

I have a WMP club date set with a beautiful even yellowing (as I said I suspect from some cause other than sunlight because both drums are the same shade everywhere) but finding a floor tom to match was nearly impossible. I've considered seeing if I could stain the floor tom to match but I don't play this set too often so why mess up a good drum?