DEET Mosquito Repellent vs. lacquer guitar finishes: Bad News!!

Finally getting back to writing some posts on my blog - and this is one that dates back to this past summer - more a cautionary tale than anything.

I was contacted by a local bassist who had finish damage on his Fender Custom Shop '55 Precision. The damage happened during a sweaty outdoors summer gig - he recounted that he had sprayed a good amount of Off mosquito repellent on himself prior to playing - and that after the gig, he realized that the finish on the top edge of the bass had become gummy where his arm had rested against the finish.

I had never heard of this happening - I theorized that it was the alcohol in the Off that had maybe just softened up the nitro a little, with the heat and sweat helping some more. Since he was local, I suggested he bring it by and I'd see what I could do - I was hoping that the damage was just in the clear coat and could basically be buffed out. I was also hoping that maybe the owner was just being a little overly sensitive about the damage, and that it really wasn't as bad as he described it.

However, when I did get to check out the bass, the damage was obvious and indeed quite bad looking - the finish had obviously gotten softened and marked up and also gotten dirt ground into it while it was soft, so it was discolored. The finish by this time (several weeks later) was hard again, but I couldn't tell how deep the damage was. The pictures below show the damage pretty clearly.




The P-bass did have a pretty good clear coat - though the damage meant I was going to have to wet sand the area and then buff it out - my worry was in cutting through the clear coat and into the translucent blonde finish, which would be almost impossible to retouch.

So I did it VERY gradually - using 600 grit wet and dry paper on a sanding block with a very light touch, and just going to the point where the discoloration was gone and holding the bass up to the light didn't reveal any unevenness in the finish. Happily I did not cut all the way through the clear coat anywhere!

From there I just worked through finer grits, all the way to 2000 grit wet and dry paper - followed by hand buffing with two grits of compound and a final "deswirl" with Meguiar's Scratch X.

As you can see, the shine came back to the finish and there really isn't any visible trace left of the damage - could have been much uglier !!





After this experience, I did a quick check online to see if maybe it wasn't the alcohol in the Off that did the damage, but actually the DEETs - and this is what I found in an article published on a University of Florida, Gainesville website:

"DEET or diethyltoluamide is an effective repellent of mosquitoes, gnats, ticks, mites, and blood-sucking flies. It has been used effectively for the past 45 years to prevent insect bites and disease transmission."

"Only apply DEET formulations to exposed skin; do not apply to areas underneath clothing. DEET will damage plastic materials, so do not apply DEET formulations on or near plastics, acetate, rayon, Spandex, synthetic fabrics (other than nylon), furniture finishes, leather, watch crystals, and painted or varnished surfaces. Plastic glass frames and goggles should be protected from DEET applications. Car finishes and interiors also may be damaged by DEET. It will not damage nylon, cotton, or wool fabrics."

So it would appear that DEETs is the actual culprit here - maybe it won't attack a catalyzed polyester or epoxy finish, but it certainly will attack a nitrocellulose finish and perhaps even a polyurethane finish.

Careful with that mosquito repellent at the next outdoor summer gig you play !!