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PostPosted: Sat Oct 06, 2007 4:21 am 
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Koa
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I went to the shop this morning to sand and buff a guitar, just when I thought I was finished I noticed some spots in the finish that looked like those you would see when trying to touch up a finish, like cloud shapes that arn't actually cloudy in color but are visible at the perfect angle in the light. They are all over the finish on the back of the guitar, the Honduran Rosewood was covered in system 3 epoxy, then finished with KTM-9 as I've done on 5 previous guitars all of which turned out fine....I'm perplexed, and totally bummed, any thoughts would be greatly appreciated.

Greg

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PostPosted: Sat Oct 06, 2007 4:29 am 
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Koa
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Was the guitar laying on any surface or was it hanging?

I'm telling you, the main ingredient in waterborne finishes is something called "wishful thinking." It should be right there on the label...


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PostPosted: Sat Oct 06, 2007 4:56 am 
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Koa
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Rick, that is funny, I'm beginning to think just like you on this subject, I believe I'm done with waterbourne finishes.

Oh, the guitar was laying flat, not hanging, I've done 5 this way whithout encountering this same problem.

Greg

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PostPosted: Sat Oct 06, 2007 6:24 am 
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I don't like KTM9.
I've had no problems with Crystalac.

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PostPosted: Sat Oct 06, 2007 7:55 am 
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Is it possible that the spots you are speaking of are areas that you have rubbed through one coat of finish to the under lying one? I've never used KTM-9 but I have seen what it sounds like you are describing in some catalyzed automotive clears over the years.

It's caused by leaving the first, or subsequent coat too long before applying the next coat. The fresh coat won't fully melt in to the under lying one. The really technical term we use for this is skinning over.

So in effect, what you are seeing is exactly as you described. A finish that was essentially cured and then another one over the top is acting like a touch up. The patches are the witness lines of the edges of the touch up. Though it wasn't meant to be one.

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PostPosted: Sat Oct 06, 2007 8:36 am 
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Cocobolo
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It also sounds like blushing in the clear but you would have seen that before buffing. Any chance we could have a look? It does sound like you buffed through a coat or two into another coat and it is leaving a witness halo.


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PostPosted: Sat Oct 06, 2007 9:38 am 
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Koa
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I'll take a few pics but I'm not sure we'll be able to see the spots. I applied this batch just like all of the rest, I waited 45 minutes between coats to the minute, put 5 coats one day(brushed)then the next day sanded and wiped with DA and applied 5 more coats every 45 minutes. I then waited 2 weeks to do the sanding/buffing which is exactly how I've done it before with fine results. The interesting thing is that I only have this problem on the back of the guitar, the top and sides are perfect. The only thing I can think of is that I put the coats on too thick and these areas did not dry properly. Oh, one thing I noticed while sanding the back this morning was that the areas in question looked different than the rest of the surrounding finish, these little problem areas had finish that seemed to stick/stay in these patches/areas and had to be wiped away where the non-problem areas were more dusty and free-flowing. Now these areas didn't seem wet or anything, they just behaved differently when sanded. I'm going to sand some more and see what happens, if I sand through, no big deal as I'm going to have to redo it anyway.

Greg

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PostPosted: Sat Oct 06, 2007 11:13 am 
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I've had those with KTM9 alos. . They loolike a spot that needs more buffing but are "inside" the layers of the finish. The last build I was meticulous about shopdust, claen sprayer and sparing application and it was OK. I'm going to continue with KTM. I have also used Flecto Diamond Wood Finish (which seems VERY similar to ktm9 TO me.)

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PostPosted: Sat Oct 06, 2007 11:14 am 
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Koa
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Are you using stearated sandpaper?   The stuff with zinc stearate that "lubricates" the paper?   It causes big problems with many finishes...

And the guitar was laying on it's back?   Another area where I had big problems...with the afore mentioned and endorsed by SteveS "Crystalac"...a finish which got me a horrendous bass review on the Internet that plagues me now to this day 12 years later. In this day and age, problem instruments never go away; they live on on the Internet to bring us down forever. Screw that. Like I've said...when Bob Taylor switches to waterbased finishes, I'll try them again.   Or if a finish company wants to pay me to test their stuff on their dime, not mine, I'll gladly experiment.   But never again on a customer's instrument for which I am responsible.


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PostPosted: Sat Oct 06, 2007 12:46 pm 
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[QUOTE=Rick Turner] ......"Crystalac"...a finish which got me a horrendous bass review on the Internet that plagues me now to this day 12 years later...... [/QUOTE]
Rick,
For a pro builder, you have a great point. For a hobby builder doing a couple of guitar a year in his garage, do you think water based finish is a good idea?
Other than send it out to a pro, what would you recommend?
What was the issue with your Crystalac finish - what was the customers big beef?
Twelve years is a long time. I suspect the the formulation has changed.

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PostPosted: Sat Oct 06, 2007 1:21 pm 
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Koa
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Rick, it was not laying on it's back, well not while I was applying the finish to the back, at a later date it was on it's back when I was applying finish to the top....are you saying that could be a problem? I'm not interested in switching to Crystallac.... really I'm looking to switch to something else, probably cat. urethane/poly.

Greg

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PostPosted: Sat Oct 06, 2007 1:24 pm 
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Koa
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I'm not sure about the sandpaper....how would I know if it's the one with zinc stearate?


I'm using some wet/dry automotive type paper and some Norton 3x.

Greg

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PostPosted: Sat Oct 06, 2007 2:18 pm 
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Koa
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They could very well have changed the formula in 12 years. Too bad I can't change what my former customer wrote...

Wet or Dry should not be stearated. The papers that appear white are.

If I were back in the position of having a small one-man shop, I'd either send stuff out to a guy like Addam Stark, put in a small booth and shoot polyester like I am now, learn to varnish as per Bruce Sexauer, or get really good at French polishing over an epoxy pore fill sealer.

The last thing I'd do would be any of the current water borne finishes.   For every claim of success, I've heard at least two tales of woe, and I can't see "It's got a water based lacquer finish" as being a selling point.

My understanding is that the guy with the best article on doing water based finishing...Mike Doolin...has switched over to polyester.   Why use what a great luthier and noted expert has rejected?


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PostPosted: Sun Oct 07, 2007 1:53 am 
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I'm certainly not an expert but 5 coats brushed sounds like a lot of material for one session - & if that's true, 2 weeks wait may not be enough. Using Ultima WB, I've sprayed 3/day and when done, waited 5 wks.


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PostPosted: Sun Oct 07, 2007 2:04 am 
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Koa
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Yeah, 5 coats may be the problem, although I've done it before and it worked fine, dunno!

I sanded the finish back to wood this morning and found it very interesting that the blotches seemed to go all the way to the wood, making me wonder if it was the epoxy that was the problem..Hmmm! But then again the problem only happened on the back, and I applied the epoxy and finish the same everywhere...just like the other guitars which had no problems...Dunno!


Oh yeah, refinishing is much worse than getting it right the first time...what a job!

Greg

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PostPosted: Sun Oct 07, 2007 3:09 am 
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[QUOTE=GregG] .......Oh yeah, refinishing is much worse than getting it right the first time...what a job!......[/QUOTE]
Greg,
I feel your pain!
My record is 3 times to refinish a guitar. I'm sure I am in good company with that and I'll bet it is no where near the record.

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PostPosted: Sun Oct 07, 2007 3:16 am 
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[QUOTE=Rick Turner] .......Why use what a great luthier and noted expert has rejected?[/QUOTE]
Because it works for me, my clients like it and ask for it when offered the choice of my water based or a pro job for $300 more.
BTW - I offer them my water based satin or Addam's gloss. One out of 10 has opted for Addam's. I even try to push them that direction and tell them how much better it will look and how much more durable it will be. I would rather send it out than do it myself. After I get a few more guitars completed, I will just start sending it out and take the option away.

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PostPosted: Mon Oct 08, 2007 12:19 am 
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Old Growth Brazilian
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I have some 15 guitars with KTM 9 on them. I have had no problems. However I to think 5 coats a day is excessive. I am not sure why you are wiping with DA as KTM is a self cross linking.

What you describe sounds like a moisture blush. Any chance that you do not have a moisture trap on your spray rig. Also putting on 5 coats a day I am amazed you don't have more blush.

I spray 3 a day for 2 days, wait 2 day level, then spray 3 more coats wait a week and level. If all is well allow to cure for 10 days and rub-out and buff.

I have never had a single blush issue.

As far as this finish only being good enough for garage builders


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PostPosted: Mon Oct 08, 2007 12:26 am 
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Old Growth Brazilian
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Humm I did not hit the post button?????

Anyway I like the stuff. It is not cat poly or nitro but it is a good finish. I personally think it is the best most dependable waterborne available. Comparing it to Cat poly , nitro or other solvent based is just like comparing them to shellac, Truth is each have attributes and detriments. I would love to have a waterborne as heard as cat poly but an apple can never be an orange.


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PostPosted: Mon Oct 08, 2007 1:50 am 
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Old Growth Brazilian
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That is one area a I do not use KTM9 except peghead veneer. My necks are either my necks are either tru-oil or Belhens Rockhard.


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PostPosted: Mon Oct 08, 2007 3:54 am 
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Koa
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I just wiped with DA per some instructions I found from LMI(I think)...they were from Mike Doolin(I think).....you know I've never really understood the DA thing either but it seemed to work for the guys writing the instructions, with lots more experience than I, so I went with it. I'm brushing these Michael, very thin coats, and I've done 5 other guitars just like this one with no problems....maybe I was just lucky before.

Greg

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PostPosted: Mon Oct 08, 2007 4:04 am 
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Old Growth Brazilian
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Wow, My experience is even the thinnest coat I could possibly apply by brushing is many times thicker than a sprayed coat. Just the viscosity of the finish causes it to brush flow much heaver than it sprays.

This is not intended to be critical, but now even more than before, 5 coats in a day is really laying it on.


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PostPosted: Mon Oct 08, 2007 4:26 am 
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The DA wipe may not be necessary, I don't know. It will aid adhesion/burning in.
You might think about thinning the KTM9 with DA to help the coats be thinner.
It will also help it burn in.
I agree with MP that your problem could be due to thick coats.

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PostPosted: Mon Oct 08, 2007 4:38 am 
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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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