Finishing workshop/lessons needed

KingCavalier · #1 08-09-2014, 11:44 AM

Hi all,

I'm currently working on my 3rd and 4th Acoustic Guitar. I finished numbers 1 and 2 with rattle cans and wanted to try and step it up a notch. I purchased an HVLP conversion gun and bought some Cardinal Nitro, sealer etc. Well, things aren't going very well. I get so much Orange peel that I have to sand back way too far between coats. I'm not sure what the problem is but I'm pretty sure It's located directly between the gun and the compressor

I live in North NJ and I'm willing to travel an hour or so in any direction for lessons. Any help would be greatly appreciated.

Please send me a PM or just post here if you able to help.

Kind regards,

Scott

LouieAtienza · #2 08-09-2014, 12:16 PM

Usually, it`s not enough.atomization, lacquer not cut down enough, or finish drying too soon. Your gun shouldcome with a viscosity tester. Also, HVLP can be trickier to get dialed in, but your atomization might be too coarse; HVLP does spray a little coarser than conventional, so your coat will lay down a little wetter. You might be able to purchase a needle and tip combo that will give you finer atomization Finally adding lacquer retarder can help the finish flow out better, though by increasing drying time.

charles Tauber · #3 08-09-2014, 01:02 PM

All the things Louie mentioned:

1. viscosity of material
2. tip/orifice size of the gun to suit material
3. too dry a coat - more fluid volume required
4. holding the gun too far from the work so that it is too dry by the time it hits the surface of the work
5. material drying too quickly to flow-out

It's largely trial and error to get the specifics of your material, your gun and your spraying technique just-so to obtain the best results. Finishing is an art unto itself.

viento · #4 08-09-2014, 01:11 PM

Just a little suggestion:
Get a peace of crap wood, plywood etc. and do some testing sprays with different amounts of thinner. I did that recently when I was up to spray a nitro burst on my first built acoustic.
I had no experience with HVLP spray guns before.

KingCavalier · #5 08-09-2014, 08:00 PM

Thanks all, I appreciate the help. I do have the viscosity cup and multiple nozzles. The .08, 1.0, 1.2 and 1.5. The Viscosity cup pointed me to the 1.2. I tested a few different mixes of thinner and sprayed around 1/2 quart on all kinds of test boards. Bottom line, I stink at this. I'm still hoping to find a workshop/lessons, a little help from a Pro goes a long way.

SA

LouieAtienza · #6 08-09-2014, 08:16 PM

Quote:

Originally Posted by KingCavalier

Thanks all, I appreciate the help. I do have the viscosity cup and multiple nozzles. The .08, 1.0, 1.2 and 1.5. The Viscosity cup pointed me to the 1.2. I tested a few different mixes of thinner and sprayed around 1/2 quart on all kinds of test boards. Bottom line, I stink at this. I'm still hoping to find a workshop/lessons, a little help from a Pro goes a long way.

SA

I think you're working backwards here. You should thin your mix such that you can use the .08 nozzle. The larger nozzles are better for waterborne finishes and urethanes, finishes that utilize a thicker build.

Ben-Had · #7 08-10-2014, 08:45 AM

I spray Cardinal lacquer unthinned with a 1.2 tip using a Homestead finishing QS-125WB gun. I get excellent results. I thin the sealer 50/50. 29PSI, 6-8" fan, 2 1/2 turns on the fluid control, gun about 6" from the work.

KingCavalier · #8 08-10-2014, 10:40 AM

Quote:

Originally Posted by Ben-Had

I spray Cardinal lacquer unthinned with a 1.2 tip using a Homestead finishing QS-125WB gun. I get excellent results. I thin the sealer 50/50. 29PSI, 6-8" fan, 2 1/2 turns on the fluid control, gun about 6" from the work.

Thanks again everyone for taking time to help me with this.

Tim, thanks for chiming in. I purchased this gun on your recommendation. I'm happy to hear it works well for you and thanks for rubbing it in

In the pics below the guitar was pore filled with Z-poxy, I sprayed 2 coats of vinyl sealer and then 8 to 9 coats (3 per session) of Nitro on the back and sides and 6 to 7 (3 per session)on the top. I sanded level with 400 grit and I still have lots of low shiny spots from what I think was the Orange peel. The pore fill went very well and after the sealer I didn't have any trouble getting it level.

I'm tempted to shoot 1 or 2 more thinned (say 50/50) coats of Nitro and call it good. Any and all thoughts would be greatly appreciated.

LouieAtienza · #9 08-10-2014, 01:30 PM

When I sprat nitro I may or may not sand between sessions depending on how well the finishlaid on. If you have orange peel after the first session I would sand flat before continuing on, because subsequent layers will make it worse.. I alao think 400 is pretty coarse for finish work; I use 800 to kevel at worst and it still cuts pretty fast.

Ben-Had · #10 08-10-2014, 09:39 PM

Here's how I'm doing mine:

Day 1 - I spray top back and sides, as soon as I am done the sides I repeat the spraying top back and sides again and then let it dry 1 hour. I repeat this series 3 more times (total of 4 spray sessions) and let it dry over night.

Day 2 - Level sand with 400 grit 3M Gold Fre-cut 216U paper (don't get aggressive around the edges and leave some shiny spots they will eventually get filled). Repeat spray schedule from day before.

Day 3 - Level sand with 600 grit 3M Gold Fre-cut 216U paper. May still be some shiny spots remaining. Repeat spray schedule let cure for 7 days (Cardinal Lacquer).

After curing I level sand with 800 grit 3M Gold Fre-cut 216U paper and then wet sand using Micro-mesh soft pads. I start with the black pad skipping the brown and green pads. Finally I buff with Menzerna Pre-polish and Intensive polish.

Along the way there may be some spots that need drop filling.