HVLP Spray systems

[B. Howard]

I have used an Apollo turbine unit for cabinet finishing for years with god results. They are noisey though. I also use the $20 HF guns with great results. To me the gun is not as important as proper spray technique and getting the viscosity and flow out of the material correct.

[tippie53]

I have a few guns and I hate to admit that my HF gun works well. As long as you can match the air flow to material , and use the right nozzle the results are pretty good. When I went from cabinets to guitars I practiced on a lot of material to learn to practice on.
I found that cardboard works well to learn how to set up the gun. Too much air and you are starting to dry the material before it hits. I like to thin down about 10% thinner and 10% retarded . This works for me. I don't spray right out of the can. I also filter the finish.
What about you Brian ? What is your thinning mix?

[B. Howard]

20% reduction sounds about right to me, I vary the amount of retarder based on the time of year and temp /humidity. Depends a bit on what retarder you use as well, I generally use some butyl-acetate. I only use enough to get good flow, generally not quite as much as John. I hang pieces of brown craft paper on a wall to set up the gun pattern, but flow out must be judged carefully. Paper and cardboard absorb the material and will appear to flash faster and not give a good read on flow out. A piece of glass will give a good read on flow out after the gun's pattern is set, and then you can just scrape off the lacquer when it is partially dry and reuse the glass. Getting good flow as the coating drys will go along way toward cutting down on level sanding and require fewer coats.

[tippie53]

thanks for the glass tip. That will show spray pattern well

[Kevin Sjostrand]

I haven't purchased this spray system yet. Still waffling. It's not the money, I just have a big air compressor and an expensive hvlp gun already, although I haven't tried the gun yet, just used regular spray guns up till now.
I will probably get it.........see, there I go waffling again!!!!!

Kevin

[Jim_H]

Mmmmmmm ... waffles =)

[Darryl Young]

I feel your pain Kevin!

[tippie53]

HVLP does a good job . It is worth the effort to learn how to set up the guns. less overspray.

[B. Howard]

I haven't purchased this spray system yet. Still waffling. It's not the money, I just have a big air compressor and an expensive hvlp gun already, although I haven't tried the gun yet, just used regular spray guns up till now.
I will probably get it.........see, there I go waffling again!!!!!

Kevin

Kevin, Nitro Lacquer is one of the easiest and most forgiving coatings to apply. If you have a good size compressor and a decent HVLP gun already I would start with that. As you gain comfort and experience you will get a better idea of what you need to better your process. If you don't already have one get a good airline filter with an oil separator. Buy a piece of 1X8 pine and some of the brand of finish of your choice and practice. When HVLP first came out years back, I hated them, now I wouldn't go back to a siphon cup for anything. Just the $ savings on materials from transfer efficiency alone makes it worthwhile, add to that less fog and stand off, less booth clean up and the ability to push heavier coatings (i.e. use less reduction, thereby spray fewer coats for the same film build) and it's all good.

[tippie53]

The only thing I can add is that, it isn't what you put on as much as what you let on. Learning to spray an even coat , and then learning to level and polish it, Having patience to allow proper cure time and then learning how to buff and polish is what can separate the beginner to the experienced finisher.
My process may be different from B Howards but this is my schedule
Sand to 220 grit. Satin or mix the stain in the filler . Maple , Cherry don't need filling. Once stained I apply a sealer . I don't use shellac as a sealer as this may cause adhesion problems . Best to use the same manufacturers product for best chemical compatibility.
So stain seal then fill . Seal and I often hit a 25% thin mix on top of the sealer within a few minutes of the sealer to get a good melt in. Then I apply finish the next day. I like to place a card at the sound hole to be able to get an idea of finish thickness application. I like to see .016 to .020 of green lacquer.
My mix is 10% thinner and 10% retarder , I may add more of one or the other depending on RH and temp. The higher the RH 1% more per 5 degree F from 70 base line. Thinner will remain the 10% unless under 65degrees then I add another 5%
I spray a coat every hr for 6 to 8 coats . I measure build on the card. Once I hit .016 I stop. This usually sinks to about .012 when cured ( 2 to 3 weeks )
Then I level sand start with 400 to 1/2 the dimples 600 at 3/4 and 800 when I bottom out. Then I spray 3 coats 10% retarder 15% thinner . Allow a cure time of 2 weeks level with 600 to 1/2 the surface dimples then start wet 800 and as I start to bottom I want to be on 1000 and work up to at least 1500 or 2000 then buff out and polish.
This is a very abbreviated schedule but you can see there is a process involved. Most of us that do this a lot will take this part very serious. The prep is so important . Plus your technique you develop is also important. Remember there is chemistry , technique and experience involved to a good finish.
I love Nitro as you can repair this anytime . Some finishes do not allow that luxury.