Official Luthiers Forum!
http://luthiersforum.com/forum/

Advice on Spraying KTM-SV Tomorrow
http://luthiersforum.com/forum/viewtopic.php?f=10101&t=30517		 Page 1 of 1
Author:  Darryl Young [ Wed Dec 29, 2010 11:23 pm ]
Post subject:  Advice on Spraying KTM-SV Tomorrow
I want to try spraying my guitar tomorrow.......high of 65 outside but chance of rain.

I have a Walcom EGO HVLP spray gun and will be spraying KTM-SV. When I poured the SV through a filter into the gun, I was surprised how thick it was. I've had the can for 3 or 4 months but it has never been opened till tonight. I'm green at using spray equipment but was able to spray shellac ok through this gun. I bought a video/book from Jeff Jewitt on using spray equipment and learned a lot from it. If I understood Jeff, if the tip is properly sized the liquid should run through the gun in a steady stream when the trigger is squeezed without the air connected to the gun. This stuff wouldn't flow out even with the trigger adjustment wide open (a drop ozzed out a time or two). This just seems too thick but others use the same gun and same tip (1.2mm) so I doubt that is an issue. I had just sprayed DA followed by Acetone thought the gun 30 min before adding the SV and those products would come out in a steady stream when the trigger was pulled with no air.

I added a little distilled water to the SV and it improved slightly. I attached the air hose and it sprayed. I adjusted it as best I knew how and sprayed some test pieces but it is not a smooth, even coat.......more like it splattered out. It was cool outside but the test samples and the gun and SV were kept inside till I was ready to spray so they weren't cold. My guess is the SV is still too thick. Thoughts? I would like to get this worked out since Thur. - Sun. I hoped to have the finish sprayed. Can I just add distilled water till it flows properly? Seems like it would take a considerable amount.

Thanks!
Author:  meddlingfool [ Wed Dec 29, 2010 11:35 pm ]
Post subject:  Re: Advice on Spraying KTM-SV Tomorrow
I had the same experience. Grafted coating recommended a 2mm tip, but that was for a porter cable gun, so I don't know if it compares. However, after building a few coats it starts to even itself out, and when I level sanded and buffed it came out fine. Just looked ugly to start and took a little extra sanding. My two cents...
Author:  Darryl Young [ Thu Dec 30, 2010 1:14 am ]
Post subject:  Re: Advice on Spraying KTM-SV Tomorrow
meddlingfool,

Did you thin the SV any before sprayimg? Do you think thinning would have helped your issue?
Author:  meddlingfool [ Thu Dec 30, 2010 2:33 am ]
Post subject:  Re: Advice on Spraying KTM-SV Tomorrow
Yes I thinned it but I forget by exactly how much. I used the formula from (I believe) Rolf Gerhardts site or possibly Randy Muthers (sp?) site. I thought of thinning it more but I didn't want to push my luck...
Author:  woody b [ Thu Dec 30, 2010 7:17 am ]
Post subject:  Re: Advice on Spraying KTM-SV Tomorrow
I don't use KTM-SV, but I've experimented with some. It needed to be thinned quite a bit. Waterbased finishes dry really quick, so it's pretty much impossible to spray without a little bit of orange peel. Thinning with alcohol, instead of water will help some. The manufacturer doesn't recommend using alcohol because they're against using flammable materials.
Author:  johnparchem [ Thu Dec 30, 2010 9:15 am ]
Post subject:  Re: Advice on Spraying KTM-SV Tomorrow
I sprayed unthined SV with a an Earlex Station Pro with a 1.5 mm needle. I had no problem spraying an even coat on the guitar, nor controling the spray patteren. With the earlex I have no option to do the test with no air as it is a continuous air sprayer.
I did end up with a hardly noticable orange peal that polished right out. When playing around trying to brush it I did thin with water. A little bit of water made a big difference in the thickness of the SV.
Author:  muthrs [ Thu Dec 30, 2010 9:51 am ]
Post subject:  Re: Advice on Spraying KTM-SV Tomorrow
Hi Darryl,

First my setup: I use a 3-stage Accuspray non-bleeding turbine gun with a #8 air cap and a 1.3 mm tip. I lot of people don't like turbines, but the non-bleeder works fine.

I have sprayed straight KTM-SV or slightly thinned as per Rofe's instructions. I would be wary if you have to thin it a lot. Waterborne is going to be much more viscous than alcohol based shellac. I'm not familiar with Jeff's test, so I can't speak to that. You want a wet coat that doesn't run. If it looks like orange peel when first sprayed that is fine, it will level. You don't want a dry coat and you want to check it 5 minutes after you spray to see if you have any runs. If so, wipe them off.

You mentioned that you cleaned the gun with alcohol and then acetone before adding KTM-SV. I would rinse it well with DI water before adding the finish to the gun. Not knowing the exact components of the finish, there is no way of knowing how it might interact with residual alcohol or acetone in the gun.

I would not thin with alcohol. Just because it worked with one waterborne does not mean it will work with another. It may work, but I wouldn't experiment on a guitar and you would have to be willing to waste a container of finish. Besides, there is no need to do it, thinning with water works fine. For example, thinning epoxy with alcohol as many do to wipe on a final coat after pore filling works. But it never gets as hard as unthinned epoxy. Of coarse it's not an issue since it's not a top coat.

Good luck.
Author:  Darryl Young [ Thu Dec 30, 2010 10:25 am ]
Post subject:  Re: Advice on Spraying KTM-SV Tomorrow
Thanks for the suggestions.

Right after spraying the finish looked like drops of finish were blown onto the surface instead of a fine, atomized spray. These test pieces were laid flat and they did level considreably so now they have an orange peel look. I will try adding a little more distilled water and recheck to insure the pressure is at the full 2 atmospheres for good atomization.

If I recall correctly, Rolf thins 3 oz per gallon which isn't much. He uses an older version of the same gun I have with the same size tip (one of the reasons I chose this particular gun). SV is an oil modified urethane. I'm wondering if there is their a limit on how much you can thin this product? Or said another way, can the qualities of the finish (hardness, buff to high gloss, etc) be affected by over thinning? I added a small amount of water last time so I'm surely not close to any limit.
Author:  muthrs [ Thu Dec 30, 2010 10:49 am ]
Post subject:  Re: Advice on Spraying KTM-SV Tomorrow
There are co-solvents in the finish to keep the resin as an emulsion. The ratio of the cosolvents to the water is important for doing that, so you don't want to add to much water. The second issue is that lowering the viscosity too much will cause the finish to run more easily. This means you will have to spray thinner coats with less build per coat. This effect can be significant.

I would really look for other problems. Clogged tip or air nozzles, etc. It only takes a little bit of finish or impurity to mess you up. What did you filter the finish through prior to spraying? I use one of those "gold" coffee filters. It works great and easy to clean.

One more thing. Those co-solvents are toxic even if they don't smell bad. The advantage of using waterbornes is that they are non-flammable, NOT that they are not toxic. No one talks about this. If you're not spraying it's not a real problem, since they are not very volatile. But once you start spraying the stuff, you need good respiratory protection.
Author:  Darryl Young [ Thu Dec 30, 2010 2:37 pm ]
Post subject:  Re: Advice on Spraying KTM-SV Tomorrow
I am using a respiratory mask rated for organic vapors so hopefully I'm ok there.

After I sprayed the SV last night I cleaned with distilled water, DA, and acetone. All of these flowed right through in a steady stream without the gun connected to air.........and the stream was straight with no twist to indicate an obstruction.

I strained the SV with filters me neighbor across the street gave me who spent his life running a body shop (self employed). He siad they were good filters and the ones he uses.

I'm about to try another coat on my test sample.
Author:  Darryl Young [ Thu Dec 30, 2010 3:26 pm ]
Post subject:  Re: Advice on Spraying KTM-SV Tomorrow
I am using a respiratory mask rated for organic vapors so hopefully I'm ok there.

After I sprayed the SV last night I cleaned with distilled water, DA, and acetone. All of these flowed right through in a steady stream without the gun connected to air.........and the stream was straight with no twist to indicate an obstruction.

I strained the SV with filters me neighbor across the street gave me who spent his life running a body shop (self employed). He siad they were good filters and the ones he uses.

I'm about to try another coat on my test sample.
Author:  Darryl Young [ Thu Dec 30, 2010 4:50 pm ]
Post subject:  Re: Advice on Spraying KTM-SV Tomorrow
I mixed up a test sample thinned 1.5 teaspoons distilled water to 1/4 cup SV which is equivalent to 4oz in a gallon if I did the math right. This sprayed very nice on the test sample so I sprayed the first coat on the body. Worked very nice and I layed down a smooth wet coat. Unfortunately, I touched up a bit too much around the waist and got a run in the top and went a little too slowly on the back and got a sag in one place. I think both of these were my fault due to spraying error.

Randy, you mentioned to wipe any runs after about 5 min so I took your advice. What do you use to wipe runs? (I aplogize for being so green that I'm having to ask simple questions like this) I was unsure so used my gloved finger on the run and tried a paper towel on the sag and it didn't look as good as the other wipe so I smoothed it a bit with a gloved finger (which looked better). I was wearing nitrile gloves.
Author:  muthrs [ Fri Dec 31, 2010 12:01 am ]
Post subject:  Re: Advice on Spraying KTM-SV Tomorrow
Darryl, glad it's working for you now. Just make sure that water is the last thing you rinse with, not the other way around.

I just wipe with a bounty paper towel. I get it while it is still wet though. It will look like it has been wiped, but with subsequent coats and leveling it is fine. If you leave a run on there it just kind of gels and doesn't get very hard. Then you have to cut it off and touch it up which is a real pain. To tell you the truth I almost never have runs anymore, but I've sprayed a lot of guitars.

One more tip. The first coat tends to run more than subsequent coats. This is because the subsequent coats tend to "sit down" on the partially cured previous coats. So I usually go lighter on the first coat.
Author:  Darryl Young [ Fri Dec 31, 2010 10:30 am ]
Post subject:  Re: Advice on Spraying KTM-SV Tomorrow
muthrs wrote:
One more tip. The first coat tends to run more than subsequent coats. This is because the subsequent coats tend to "sit down" on the partially cured previous coats. So I usually go lighter on the first coat.


I sure agree with this statement. 90% of my issues were on the first coat. I had the gun adjusted for a little too much spray and went a little too slow (trying to get an even coat with thorough coverage) and ended up with way too heavy a coat and it sagged in places. I wiped what I saw but missed a place or two as I was concerned about getting my gun cleaned. 2nd coat was perfect. 3rd coat a little light and 4th coat about right.

I stopped at 4 coats since the first coat was so heavy. Everything appears to have cured properly. Now I get to see how well I can sand off the sags/runs without sanding through adjacent areas that aren't extra thick from a sag.

I must say, I'm impressed how glossy this finish is. And I must admit most of my problems were beginner issues from spraying an instrument for the first time........not problems with the SV. I'll start level sanding right after breakfast and then try to spray 2 or 3 more coats.
Author:  paul h [ Sat Jan 01, 2011 8:50 pm ]
Post subject:  Re: Advice on Spraying KTM-SV Tomorrow
Darryl - what did you end up using for a sealer under the SV, and did the guy from Grafted ever report on their experiments with different sealers for rosewood and other oily woods?

Thanks, Paul
Author:  Darryl Young [ Sun Jan 02, 2011 12:36 am ]
Post subject:  Re: Advice on Spraying KTM-SV Tomorrow
I used a thin coat of zpoxy as the pore filler. Probably would have left a thin coat anyhow so the color was consistent.

To answer your other question: no, they haven't reported back with the test results. Hopefully they will report back soon.

Here is a pic of the guitar before the last coat was sprayed:
Attachment:
After 6th Coat.JPG
Author:  woody b [ Sun Jan 02, 2011 9:07 am ]
Post subject:  Re: Advice on Spraying KTM-SV Tomorrow
Randy, Darryl, or anyone else, are you scuffing KTM-SV between coats? I'm just curious.
Author:  muthrs [ Sun Jan 02, 2011 10:10 am ]
Post subject:  Re: Advice on Spraying KTM-SV Tomorrow
No scuffing between coats, except to knock off the occasional dust nib. On day two I level sand after the first set of coats before spraying the second set.
Author:  muthrs [ Sun Jan 02, 2011 10:13 am ]
Post subject:  Re: Advice on Spraying KTM-SV Tomorrow
I've been asked by Grafted Coatings to do some tests with their experimental waterbased sealer. It will probably be close to a month before I have anything to report.
Author:  Darryl Young [ Sun Jan 02, 2011 10:48 pm ]
Post subject:  Re: Advice on Spraying KTM-SV Tomorrow
woody b wrote:
Randy, Darryl, or anyone else, are you scuffing KTM-SV between coats? I'm just curious.


I didn't scuff between coats Woody. Just finished level sanding with P1000. Too tired to sand through higher grits today so will sand to 2000g with Abralon pads tomorrow.

Randy, I missed a couple spots when I was drop filling. Do you have any suggestions to fill now? Any chance I can fill these couple of spots with CA? They are small so not a big deal if I leave them as they are now.
Author:  muthrs [ Sun Jan 02, 2011 11:30 pm ]
Post subject:  Re: Advice on Spraying KTM-SV Tomorrow
Darryl, I would just drop fill them with finish. May require a couple of applications, then level sand the next day and wait seven days before buffing as you would the rest of the guitar.
Author:  meddlingfool [ Mon Jan 03, 2011 4:02 pm ]
Post subject:  Re: Advice on Spraying KTM-SV Tomorrow
I found CA turned opaque white when used as drop fill
Author:  GRAFTED_COATINGS [ Tue Jan 04, 2011 1:54 pm ]
Post subject:  Re: Advice on Spraying KTM-SV Tomorrow
To answer a few questions and not take over a thread that is a very good read.

Distilled water verses DA or Acetone: We have always suggested water over anything else. As to why, keeping a system non-flammable is our goal. Adding DA or acetone increasing that level of flammability. Reading forums over the years, DA/Acetone has been added for between days as to create a "burn-in" effect of the coats. The more water, acetone, DA you add to the coating, the lower the solids per coat and VOC.

Spraying out of a 2mm tip as we do, the viscosity is perfect. Spraying out of a smaller tip size may or may not need adjusting. Based on reading, luthiers want a much thinner spray and with that as mentioned above can cause runs, drips etc. Very small percentage of Rheology modifier (thickener) is added to stabilize that system and helps with alongside with the co-solvents. Remember, water is considers a solvent as well.

Daryl, sounds like the product is working out for you so far. As with any product or switching from one to another is always a learning curve

For testing a sealer product, that is in the works with a few samples out in the field and awaiting results.
Author:  Darryl Young [ Tue Jan 04, 2011 5:26 pm ]
Post subject:  Re: Advice on Spraying KTM-SV Tomorrow
GRAFTED_COATINGS wrote:
Darryl, sounds like the product is working out for you so far. As with any product or switching from one to another is always a learning curve.


I am very happy with the product so far. And yes, I would say all the little issues I faced were caused by my lack of spraying experience and had little to nothing to do with the SV. It looks great after sanding to P2000 with Abralon pads. I'm anxious to see it after it's buffed out.
Page 1 of 1 All times are UTC - 5 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/