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KTM9 Over Lacquer?
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Author:  cyrguitars [ Sat Dec 13, 2008 7:31 pm ]
Post subject:  KTM9 Over Lacquer?

I have a bass body that has two coats of McFadden's Sanding Sealer on it so far. But I'd like to switch to KTM-9 waterborne lacquer now. Can I just apply it over the sanding sealer?

Thanks!

Author:  Dave Fifield [ Sat Dec 13, 2008 7:48 pm ]
Post subject:  Re: KTM9 Over Lacquer?

I'd slap on a coat of shellac first.

Dave F.

Author:  Kent Chasson [ Sat Dec 13, 2008 10:08 pm ]
Post subject:  Re: KTM9 Over Lacquer?

I've never tried it but conventional wisdom is that waterbourne under solvent based is OK but not the other way around. Solvent based finishes continue to off-gas for a long time. If you put an impervious film over it, the gas can't escape and problems arise.

Author:  cyrguitars [ Sun Dec 14, 2008 1:56 am ]
Post subject:  Re: KTM9 Over Lacquer?

So it sounds like I should strip off the sanding sealer, yes? I guess I'll attack it with some lacquer thinner tomorrow.

Thanks y'all!

--Steve in Roseville

Author:  Dave Fifield [ Sun Dec 14, 2008 4:01 am ]
Post subject:  Re: KTM9 Over Lacquer?

I would just sand it (220 grit) back to bare wood again, not strip it chemically. The little bit of sealer left in the pores of the wood isn't going to be an issue IMO. I would then seal it with shellac before moving on to finish.

Dave F.

Author:  Robbie O'Brien [ Sun Dec 14, 2008 11:21 am ]
Post subject:  Re: KTM9 Over Lacquer?

How about if you do a test piece on some scrap and see if it works. Then you could report your findings to help others in the future.

Author:  cyrguitars [ Sun Dec 14, 2008 9:48 pm ]
Post subject:  Re: KTM9 Over Lacquer?

Dave Fifield wrote:
I would just sand it (220 grit) back to bare wood again, not strip it chemically. The little bit of sealer left in the pores of the wood isn't going to be an issue IMO. I would then seal it with shellac before moving on to finish.

Dave F.


Sounds easier and less toxic than my lacquer thinner approach, so that's what I'll do. I don't have any shellac - is that a necessary step?

--Steve in Roseville

Author:  Michael Dale Payne [ Wed Dec 17, 2008 11:50 am ]
Post subject:  Re: KTM9 Over Lacquer?

the thought process is to seal the nitro and give a layer that the waterborn will adhere to . But frankly I too fear that the nitro is still gasing which will cause big issues.

If me I would finish out in nitro but if you really want to go to waterborne then I would remove all finish and start over if i was to put KTM9 on this guitar

Author:  cyrguitars [ Fri Dec 19, 2008 3:10 am ]
Post subject:  Re: KTM9 Over Lacquer?

That's what I've done - sanded it down to bare wood. The next step is to seal it with epoxy in preparation for the KTM-9. I'll do that tomorrow, then start applying KTM-9 on Saturday.

Thanks again for the advice!

--Steve

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