Nitro Problems

[Rick Matei]

For years I have used ML Campbell vinyl sealer and their nitro lacquer, with good results. My Edmonton, Alberta, Canada industrial supplier has switched to their own brand name and told me it was comparable. I used it on two new guitars I built. These guitars received my usually application scheme and were left for 6 weeks to cure before rub out. Last week necks were attached, bridges installed and the guitars were completed. Two days later I noticed severe finish cracks radiating on the lower bout, specifically spider web cracks going in all directions from the rear of the bridge back. It appears that the finish can not take the flex and vibration. Finish is always a pain, so I want to use the best materials available. From your experiences who makes the best vinyl sealer-nitro combination of products.    

[chris snyder]

What is the "my usually application scheme?" Mainly from spraying vinyl to first nitro coat time line.

[Rick Matei]

Thanks for asking.
One coat of vinyl sealer, front and back, cure for 2 hours. Scuff with 400 grit then one thin coat of vinyl let stand for two hours, then 2 coats of lacquer one hour apart. Next day scuff sand and fill pits with lacquer, four hours later apply three coats of lacquer, two hours apart. Third day, scuff sand and apply two more lacquer coats. I am trying to keep finish thickness down to less than .008.

[chris snyder]

I might be a time issue. I know that some folks, using McFadden system, would wait no longer than 30 min befor 1st nitro; sprayed right on, no scuff. Is there any "lifting?" Can you pull the finish off the guitar with ease?



Keep in mind that everyone has their own way of finishing that might not translate well.

[Rick Matei]

Chris. if you stand right in front of the guitars from two feet away you can't see the cracks,the guitars look perfect, but turn the guitar to get the reflected light and whamo they stick out like well you know what I mean. If you run your finger over the surface you can barely feel the separation. The finish will not flake or peel. It has the look of your regular lacquer crack, similar to the one that Frank fixed on a new guitar on Frets.com. I've just got more of them. Under the magnifier they are a white as white can be. What lacquer brand are you using?

[chris snyder]

Turth be told, I never once sprayed for the company i worked for. I did inspections for finish and buffing dep. and buffed. We did use McFadden, they went under, then used Mohawk; which the worst adhesion; you could pull the lacquer off with your fingers. We used others as well that did not work.

I know you want to switch, but...
What I was trying to figure out is it product or method. Finish is more chemistry than anything else; the product just might not work for your application (this is what we were told by a large manfacture) or it might not work well with your method. This is true with most Nitro from different companys, even if they buy the rights to the formulas.

Any way you go you will need to change. Try calling the company that makes the Nitro and ask for the chemist that over see the product/developed, tell them the issue, you are most likely not the only one with this problem, they just might have the answer your direct problem. This is how big manfactures get what they want out of their finish.