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?? on refining application technique with KTM-9
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=28577		 Page 1 of 1
Author:  lneal14513 [ Tue Aug 10, 2010 12:59 pm ]
Post subject:  ?? on refining application technique with KTM-9
Here's what we use:
Devilbliss FLG3 gravity conversion gun
12-15 lbs pressure
approx 4-6" from the instrument

We can't seem to reduce the amount of "pebbling" in the finish that needs to be sanded after curing. I think this is part of the reason we have problems sanding through. I've read various posts on other forums where folks suggest adding a little everclear to the finish in order to get a more matte looking end result.

Anyone have any experience with or advice for someone wrestling with this problem, or ratios of alchohol to finish?

Thanks very much!
Author:  Andy Birko [ Tue Aug 10, 2010 4:13 pm ]
Post subject:  Re: ?? on refining application technique with KTM-9
I don't spray KTM-9 but I do spray Target USL and since no one's jumped in, I'll at least tell you what I think. First I'll warn you that I am a novice at spraying finishes with only 4 under my belt though they all came out really well.

First, when you say "pebbling" do you really mean pebbling or do you mean orange peel. I've attached a shot of what my finishes look like off the gun. I'd say that my finishes have some orange peel but don't have pebbling.
Image


I did have some pebbling in the begining when I was using an HP gun. The solution was to open up the fluid needle. The problem was described that I'm probably getting some finish that's drying in the air before it hits the surface. Opening up the fluid needle did indeed help. I sanded down the pebbling and sprayed with more fluid and it worked fine.

If it's orange peeling that you've got, apparently the fix is a better gun and a different finish. e.g., apparently nitro OPs less than acrylic. EM6000 less than USL.
Author:  alan stassforth [ Tue Aug 10, 2010 5:41 pm ]
Post subject:  Re: ?? on refining application technique with KTM-9
try cutting down your material flow to a finer mist.
i have had that same prob, and just grind through it with sandpaper.
i ain't da best sprayer in da world though.
i just shot 2 coats of that stuff yesterday.
good thing they make sandpaper.
i also wish nitro wasn't so nastay.
Author:  lneal14513 [ Wed Aug 11, 2010 3:40 pm ]
Post subject:  Re: ?? on refining application technique with KTM-9
Thanks for the advice guys! We should be spraying in a few weeks again. I'll let you know how it turns out, and if I gain any useful knowledge I'll pass it along.
Author:  Andy Birko [ Thu Aug 12, 2010 7:01 am ]
Post subject:  Re: ?? on refining application technique with KTM-9
So you have two pieces of advice that exactly contradict each other - are you going to try both and let us know which works?

I don't think that sending less fluid into the mix is going to help, it's going to make things worse. You need to get more finish on the surface so it can flow out more but obviously, not so much you start getting runs.
Author:  lneal14513 [ Thu Aug 12, 2010 11:48 am ]
Post subject:  Re: ?? on refining application technique with KTM-9
I am going to try both pieces of advice--on large test pieces. We've recently resawn some african mahogany boards. I'm going to be doing pore-fill tests with egg whites, and test shoots with both suggestions.

I will happily share the results (with pix), the good, the bad, and the ugly.
Author:  Darryl Young [ Thu Aug 12, 2010 12:26 pm ]
Post subject:  Re: ?? on refining application technique with KTM-9
Hopefully, those test boards will be dry. I'm guessing the way the finish acts and cures would be different on a "greeen" board.
Author:  bluescreek [ Thu Aug 12, 2010 1:53 pm ]
Post subject:  Re: ?? on refining application technique with KTM-9
Do you have a water separator on your sprayer . When you see this you most often have too much air. What you are doing is actually starting the drying process at the nozzle. Read your manual you got with your gun and see what they tell you to do. You may need to add a retarder .
Author:  Stuart Gort [ Thu Aug 12, 2010 3:45 pm ]
Post subject:  Re: ?? on refining application technique with KTM-9
Andy Birko wrote:
Image

The problem was described that I'm probably getting some finish that's drying in the air before it hits the surface. Opening up the fluid needle did indeed help.


I'm not familiar with "USL". I just got a gallon of EM6000 though. I assume they are similar products.

More material might help but a little thinning will help atomize the material better as it goes out the nozzle. Could be your nozzle orifice diameter is too big for the material type as well (my best guess here). If it is, there isn't much you can do to with the other variables to really get rid of this though you may find workable settings. My guess is that your material will go on a heck of a lot smoother if the orifice size is correct for that viscosity.

If the material you spray won't cure in a few minutes in a thin film on a piece of cardboard....it's not curing in the air on the way out of the gun. If the thin film cure time is longer than a few nimutes, the material is probably not atomizing properly.

Target Coatings should be able to recommend the proper orifice size, delivery system, and pressure to use for their products.
Author:  lneal14513 [ Sun Aug 15, 2010 2:04 pm ]
Post subject:  Re: ?? on refining application technique with KTM-9
The boards have been at 70/40 for a couple years. They are dry and stable. We actually have 2 water separators at points from the compressor to the gun. We do still have the manual and are studying it (all 8pg, written by someone for whom english was obviously a third or fourth language). Of course we should have done that in the first place. We may well end up replacing the needle valve or other parts which upon VERY close inspection have some wear.

On test pieces of cardboard it dried to a film reasonably quickly, and on instruments also. We just need to experiment and take careful notes on the results. The finish looks great, but it was a painful process to get to that point so we need to take some time and labor out of the mix if possible. We all LOVE guitars and love building, but nobody wants to sand 8 hrs a day for a month on 5 instruments with 3 re-shoots.

We also may try a retarder as well. Upon further review of the manual, the spray pattern we get on cardboard isn't the shape it should be, and it indicates too much air, as John and some others suggested.

I really do appreciate everyone's input and I'm going to the shop tomorrow armed with a decent camera and a good dose of resolve to fix this problem. I will happily share the results.

Thanks again.
Author:  woody b [ Sun Aug 15, 2010 3:43 pm ]
Post subject:  Re: ?? on refining application technique with KTM-9
Disclaimer: I don't use waterbased finishes, but the same techniques should work


The picture in Andy's post can be helped or eliminated by

1. Thinning the material.
2. Opening the fluid control some, or using a bigger nozzle
3. Moving the gun slow across the surface.


Again, this is what would fix this with most finished. I don't see why waterbased finishes would be any different.
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