Help requested for a poly finish!

[Jerry Ryan]

I have a Guild GAD 50 with a poly finish. After repairing breaks and cracks, it needs the entire top refinished to achieve a decent finish. Am I going to be able to get a finish that will stay using 1# shellac as a bonding coat before applying a nitro finish? I keep reading about nitro coming off after time in these applications? What about KTM9 which LMI carries?

Jerry

[Bob Webster]

Jerry, are you completely removing the old poly finish prior to the shellac step? If so, you should have no problems getting either nitro or KTM9 to stick to the shellac. I've done both and the results have been just fine, as far as adhesion goes. If I can editorialize, though, KTM9 is just not in the same league as nitro from ANY standpoint except VOCs. Spraying KTM9 is like shooting stucco on a house and the stuff needs tinting to get away from a hazy blue cast in the dried finish.

Bob

[Jerry Ryan]

Bob,

I am planning to leave the orig poly finish on, just prep for the new top coat. Whatever that should be. What this pic doesn't show is that after the next step the black sunburst ended up with wood showing thru on the crack lines near the tail.

The pic shows what I ended up with after the initial crack, break repair wirh superglue and scraped. Since 1/3 of the top is involved I thought I should re-coat the entire top after touching up the black sunburst previously mentioned. To avoid 'blending' two finishes.

I had some serious cracks on either side of the end pin (about 6-8") either way, and I did use 1# shellac as a bond coat and then a couple of coats of nitro to re-finish the sides and that turned out good.I believe you advised me of the method for that. But I am hesitating on the top. I don't want to end up with the new layer of nitro to separate in a yr or 2. I'm planning to keep this rescue project for myself if it has a good flatpicking tone!

Jerry

[Bob Webster]

I know alot of people just swear by shellac's ability to stick to anything and I shared that faith until I recently saw shellac lift off of a superglue coated surface with little coaxing (draftsmans' tape). In retrospect, it probably would have done a better job of sticking if I had scuff sanded the CA before I started putting down the shellac.

In truth, I don't know of any alternatives to what you plan to do. Shooting more poly isn't the way to go. Given your success with nitro on the tail of the guitar, you might as well follow through on your plan. Did you do any scuff sanding in that instance? Best of luck with the sunburst. Yet another reason why I only do classicals any more:~).

Cheers,
Bob

[Jerry Ryan]

Bob, yes, I sanded it with 400 then sprayed the shellac and then the nitro. guess I'll try it. I'll let you know. Thanks, Jerry