Acoustic Guitar Construction

johnparchem wrote:It is still Target EM6000. I have found with good control of each spray coat the color is great. The thickness of the individual coats seem to matter more than the number of coats when trying to avoid the WB blue tint.

I stopped using EM6000 because of the blue tint/haze. How did you eliminate it? I still have a gallon left.

Tim,

I use a mill gauge to set my spray gun and keep each coat to 3 mill wet. I learned this after I ended up with a completely blue instrument with EM7000 (faster build product that really shows the problem).

I also use zpoxy on everything but the top but wash coat the top with shellac. Both have an amber tone which may mask any remaining blue.

Here is EM6000 all buffed out. In real life it looks a little different the nitro, which I think has a bit more clarity. But over all I am quite happy with the look. I do not see the blue. You can see the white plan in the background so the color balance is pretty accurate in these shots.

John, that is beautiful. I've been using EM6000 but I can't seem to achieve the mirror finish that you have. Can you tell me your finishing process from pore filling to sanding and buffing? Finishing has always been the toughest part for me.
Thanks,
Jim

I prep sand the instrument to 180 grit using a random orbital sander.

I use zpoxy to pore fill the back and sides, I apply and sand 400 grit multiple times until the pores are full, usually 2-3 coats. I actually sand to level no shinny spots so I may end up sanding to the wood on any of my applications. I finish the zpoxy with a wiped on diluted zpoxy coat diluted with Denatured Alcohol or Everclear to assure even color if there are sand throughs. I dilute the zpoxy 20-30% after it is mixed.

I almost always pad on 2 wash coats of blond shellac to the entire instrument. I like the slight amber coat and it provides a seal between the zpoxy and the lacquer. From a color perspective I have found that having the subtle amber shade as a common color allow the various wood components to look good together visually.

I spray up to 8 coats on the top and 16 coats on the back and sides. I am very careful setting up my qual spray QS-125WB (really a touch up gun, only needs 4 CFM at 40 psi) so that I am getting 3-4 mil wet coats. If I did good prep I will spray all the coats with out leveling, 4 coats a day an hour apart. At 4 and 8 coats I check how the finish is being applied, I will do any drop fill if necessary and sand level if I find any flaws. I find when spaying at that thickness I get really good leveling and no runs or sags. While learning I found that EM6000 can be sprayed thicker without runs or sags but will show a blue cast.

I let the instrument sit for a week and use a random orbital sander with a 600 -> 800 - micromesh 1500 - 1800 - 2400 disks. I sand dry.

Probably the biggest contributor to the mirror shine is that I have a stewmac buffing station and use menzerna medium and then fine.

John, micromesh has several different type abrasives, which product numbers are you using for the 1200 to 2400? And you are using them dry, not wet sanding?

Tim, here is the product I buy, I did make a mistake above I start with 1500 not the 1200 I wrote previously.
http://www.amazon.com/MICRO-MESH-8-HOLE ... B000H6JDDM I use these dry with a vacuum attached to my ROS. These are all shades of gray, not the color coded ones.

I went down and looked at my disks and I have sanded higher but I know the last few instruments I only went up to the 2400.