Box lacquer and rubber: bad reaction...

[Morocotopo]

Hi guys, want to tell you about something I discovered last night: Rustoleum spray clear lacquer reacts badly with rubber.

I`ve been finishing my boxes with Rustoleum. Yesterday I was looking at some pedals whose knobs were feeling sticky. I thought that the knobs were sitting too low, so I took them off and I discovered that the rubber in the knobs reacted with the lacquer wherever they touched and the lacquer become soft and, well, rubbery. Also, any spot where the patch cables (also made of some kind of rubbery stuff) touched the box, they became stuck together and the lacquer softened.
Grrr!! I´ll have to get some cloth covered cable and remake all my patch cables...not nice. And change all those knobs.

Anyone had the same experience? I´m thinking about an alternative finish for the boxes. Is there a clear epoxi based lacquer that comes in a spray can? Some previous boxes I finished with a two part epoxi lacquer, but that has to be applied with a brush, so it shows some brush stroke marks when finished.

[deadastronaut]

hmmmmm...sounds like a nasty mess..

i use car laquer in spray cans...no problems...nice finish too...

goes hard as glass when baked...

[Morocotopo]

Could you tell me the brand/type of stuff you use?

[~arph]

Sounds like a common thing. The solvent in the laquer (that makes it liquid) also works as a solvent for other materials. Rubber and plastics are sensitive to this. Should not be a problem when the laquer has fully dried (about a week I guess) as all the solvent will be evaporated by then.

[Morocotopo]

Arp, the boxes have been finished for months, I gues the solvent should have evaporated already...or not? I believe (just speculation) that some chemical in the rubber softens the lacquer.

[~arph]

Mmm.. then perhaps there are solvents in the rubber to keep it flexible. I recall having some rubber fishing lures eating away a plastic box they were kept in.

[Philippe]

Rubber & lacquer finishes don't bode well together...just ask anyone who has had the misfortune of leaving a nitrocellulose-finished guitar on one of those guitar stands with surgical tubing. The evaporative agent in the lacquer reacts badly with the rubber, dissolving it along with the finish. Poly finishes use a catalyst instead of acetone so the finish hardens while drying rather than via an evaporative process. An evaporative-type finish while stable/usable within a month can take years to completely harden.

So avoid rubber knobs if they are to come in contact with a laquered finish...use hard plastic ones instead & maybe consider raising them a bit above the surface of the enclosure.

[Morocotopo]

OK Philippe, now you´ve made me paranoid about my guitar stands...



They have a sort of rubbery thing in the "hooks" where the guitar sits... could that be plastic? How do you distinguish plastic from rubber?

[Philippe]

...They have a sort of rubbery thing in the "hooks" where the guitar sits... could that be plastic? How do you distinguish plastic from rubber?

Surgical tubing is kind of yellow-orange & 'rubbery'...the same stuff often used (in a smaller diameter) as heigth springs underneath your Stratocaster pickups.

[Morocotopo]

Oh, ok, I´ve seen that. My stands have a black thing, not rubber-like as microphone cables, but less, hmm, matte. Hopefully the manufacturers used safe materials...

Back to the subject matter, would anyone reccomend a non reactive lacquer?  Is the nitro type the one that reacts? Polyurethane lacquer doesn´t?

[Philippe]

Back to the subject matter, would anyone reccomend a non reactive lacquer?  Is the nitro type the one that reacts? Polyurethane lacquer doesn´t?

Modern automotive paint works well. Due to environmental constraints, most of them are of the catalyst type. The use & availability of nitrocellulose lacquer (for stuff like autobody work & hobby/woodworking use) is pretty restrictive these days.

You might try some Duplicolor. It's a generic autobody touch-up paint that comes in an aerosol, readily available at most aftermarket car parts stores & it comes in an assortment of different colors. I've used it frequently as a stompbox color coat (over gray or white primer). Holds up reasonably well (although I have recently switched to powdercoated Hammonds...eliminates priming/painting).