PVC & Nitrocellulose Lacquer: Do they react?

[John Cartwright]

Greetings, haven't been on in a good while, but I'm still here!

OK, so I have a question that is a bit off topic, but a little bit related on account the finish/chemistry issue I'm faced with. I hope it's OK that I'm asking here, I would have asked elsewhere, but I really trust you guys, and your expertise, so here goes...

I recently purchased a fantastic vintage desk by Standard Furniture Company, probably 1940's, and from solvent tests, it appears to be nitrocellulose lacquer (softens with lacquer thinner and a Q-tip, reacts only a little with alcohol and the same method) I'm currently reviving the the top with a light sanding to level, and a fresh French polish with de-waxed shellac from LMI. Now, I wanted to protect the top with a clear desk pad that showcases the grain but gives an extra barrier in the work area of the desk. After receiving the desk pad from Amazon, I see now that it is made with a semi-soft PVC. My first thought was 'great, I might as well throw a bunch of vinyl Ace guitar straps on there and wait for the melt!'

I looked up the differences between vinyl and PVC, and while they are related, they are different, but all technical notes I've read give me no clue as to whether or not it is safe to use this desk pad, or to send it back for a polycarbonate one.

Thoughts? ...and Thank You!

-John

[Howard Klepper]

the problem is not the vinyl or PVC.  "Hard vinyl" such as Boltaron or the stuff Gibson used to use for archtop pickguards is OK. What you need to avoid is the plasticisers added to give vinyl flexibility.  They migrate to the lacquer and ruin it.

But shellac is a good barrier, and may protect the lacquer from migrating plasticisers.  I wouldn't want to guarantee that, tho.

[John Cartwright]

Howard, it's interesting that you mention these plasticizers. I was just talking about the project with one of my wife's friends, and she mentioned the plasticizers too, but for different reasons. According to some research she's done about chemicals in the home, these plasticizers continue to off-gass which isn't great for one's health, especially in confined spaces like bathrooms. For this reason, she has sworn off ever purchasing a PVC shower curtain again. 

Thanks for your comment above. Good info!

[Richard Bales]

There's a type of "plasticizer" in your natural skin oil - it's what keeps your skin supple and leads to that softening of the lacquer where your arm rests on your favourite flat top.  So better keep your skin out of the bathroom too.  :-)

[John Cartwright]

(palm slapped to forehead) Oh man! ...I just can't win.

;-)