Hello all.
Since this is my first post to this forum I'll give you a little context about myself so that you can judge my comments for what you might think they are worth based on my limited experience. Mostly I promise to do a lot more listening here than speaking out.
I've now built just five guitars. I've had good feedback on them from friends, some very good players, and guitar sales people. I currently have "orders" for three more. I put "orders" in quotes because the people that want them are friends and I'm only asking that they cover the cost of the materials - I'll take the quotes away if the day ever comes when I build for a stranger and for a profit, however modest. Anyway, the point I'm trying to make is that I've gotten some independent and positive feedback on my efforts to date in order to try and obtain even a little bit of credibility here. Now on to the topic at hand.
The last four guitars I built, I fnished with KTM-9. I've just about concluded that I've been wasting precious time trying to get good with this stuff. It's just too soft and, careful as I have been, I have found it impossible to finish without having scratches somewhere from what I would consider normal handling during sanding/polishing. Other problems I have had include lack of clarity, bluing, sanding through and sinking into joints. Up to now, I've been willing to chalk these problems up to my inexperience but enough is enough. The last guitar I did I sanded through in a few spots trying to chase away the shiny spots to be sure I had it all level. OK, my bad. So I accepted that there were going to be some witness lines from where I repaired the sanded through areas. In the end, the finish was what I would call not great but acceptable. Other people looking at the guitar seemed to think it was very nice. My favorite salesman seemed to really like it and asked me how I got that slightly smoky aged look in the finish - as though I was trying!! Anyway, this past week end, I took it to Toronto to give it to my son (for whom I built it) and by the end of the week end I could see what looked like a fine crack in the finish all the way up the back of the guitar along the center joint. I can only guess it was initiated by a change in humidity level. I can't tell you how much this bugged me. On the other guitars I've used this on, I can feel where the finish has sunk into some glue joints and on one other there appears to me cracks. I know humidity control is important, but I don't think I've subjected the guitars to extremes and I think they have to have some tolerance to the real world.
The last few years there has been an excellent guitar show in Montreal that I've attended. I've searched out luthiers that have finished their guitars in KTM-9 and run my hands over their guitars. Inevitably, I can feel where the finish has sunk into the joints. So it's not just me. So I know that even if I manage to perfect my technique and start off with "perfect" KTM-9 finishes, if I stick with KTM-9 my guitars will be always be prone to finish shrinking in at the joints and, now I'm convinced, cracking (which may be an equivalent thing - I'm describing how it looks).
The last two times I was at the Montreal show, I was able to talk to Mike Doolin for a bit (he was pretty busy showing people his very cool arch-top harp guitar). The first time, I asked him why he switched from KTM-9. He said he was tired of a finish that could be marked just by doing this - at which point he tapped the top of his guitar with his finger nails. He also said that he had some customers ask him to remove the KTM-9 and apply another finish. He said it comes off easy with a little heat. When I asked him why he went to poly instead of nitro, he just said "I sort of skipped that step". The second time I saw - just this past July - I asked him if he knew any way that I could prevent the KTM-9 from sinking into my glue joints. He responded that to do that I would have to always keep the guitar in a constant humidity environment. In fairness, I must also add that he expressed the opinion that KTM-9 offered better resistance to sweat than other water based coatings that he had tried and that for me, a hobby builder doing only one or two guitars a year, KTM-9 was the way to go. However, when I ask myself if I think I'll ever be totally comfortable building a guitar to sell finishing with KTM-9 or even if I myself would ever buy a guitar finished with KTM-9 I have to at this point say no.
So I've decided it's time to explore other options that are possible without a spray system. Bill Cory over at kit guitars recommended Min Wax Wipe On Polyurethane and I have to say on the test pieces I've tried, it doesn't look too bad. It doesn't have the "under glass" look of KTM-9 but it sure is easy to apply and turns out very glossy and wonderfully hard. I know this is not the finish of choice among luthiers but I don't know why. Is there any reason not to use wipe on polyurethane? I'm also thinking I should learn to French Polish. If a problem with polyurethane is that it harms the tone of a guitar, would there be anything wrong with a guitar that had urethane on the back and sides and was French Polished on the top?
Sorry for the rant - I hope it had some useful information for some people and thanks in advance to anyone that replies to the questions I had at the end.
Pat
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