HVLP Spray systems

[B. Howard]

With a few subtle differences I do mostly the same as John.

I prep sand to 180 rather than 220 to get better anchor for the sealer. You should stay with products from the same manufacturer and system. That way if you would have a problem their tech dept will be able to assist you. Also most modern formulations really do require it.

John's measurements are for total film build to be at about 0.020" green, I look at things from a per coat build and generally like to hang about 3-4 mills per coat, wet. I measure that with a mill card if I need to. I will split my initial film build into 2 stages, applying about 4-5 coats the first day. Wait 2-3 days depending on conditions and give a light level sand with 400. I am only looking to remove 30-40% of the dimples here at most. Then spay another 4-5 coats. The last of these coats will be a "flow coat" I generally add a little extra retarder to the pot for this, maybe 2-5%. This is based on amount of mixed material in the pot and not on initial mix volumes. I spray this flow coat as heavy as I dare, trying to hang 4-5 mills. The idea here is to get that coat to flow out as much as possible before it flashes. For me this goes a long way toward cutting down on the amount of level sanding at the end. This will cure for about 4-5 weeks. At this point I will level sand much the same as John and buff. I find this gives me enough film for buffing without the additional coats, but I should point out I hand rub the finish and do not use a buffer on a arbor so I am not removing and pushing around the coating that aggressively.

[Kevin Sjostrand]

An update: I did purchase this spray system from Rockler. It hasn't arrived yet and it will be probably April before I use it. I will for sure let you all know how it goes when I do the first spraying. I figure for a $100 I don't have alot to loose if it doesn't work out, but the indications are that it should spray nitro just fine when properly thinned.
I may have a very expensive new HVLP gun for sale!!

Kevin

[Darryl Young]

Let us know how you like after you've used it.

[Kevin Sjostrand]

My sprayer arrived yesterday. I'd say from looking at it that it should work!!!

Kevin

[naccoachbob]

This thread is part of what I've been looking for. Great information about the finishing schedule.

John Hall, on the 2nd page, the last post, you started talking about changing your percentage of thinner and retardant based on RH, but you went to temperature.

Could you go over all that one more time for me maybe covering the RH first, then the temp?

Here in East Texas, my RH is usually higher than what you'll see in the Poconos, or for that matter, anywhere else in the universe, so I'm particularly concerned with that. I do not have any means of controlling the humidity. I just have to take advantage of days when it's good.

Another question. I'm seeing where some are talking about using nitro to spray finish. I understood it to be pretty volatile. What precautions to you use to keep the danger down? If you're an amateur builder/finisher, do you use a knock-down booth? What's your ventilation?

I'm going to start wet sanding and buffing out a nitro finish that I did from rattle cans, so I'll have some sense of whether I like that type finish or not. Of course that leads to other questions about all the different types of finishes to spray on. But I'll pester ya'll later.
Thanks, Gang for the info.
Bob

Oh and Kevin, have you got to use the new gun this spring yet? How'd it do?

[tippie53]

the RH can make you change things a bit , the more moisture the more you want to thin the mix. Keep the retarder about the same. If you see it starting to blush ad more thinner and spray lighter coats.
Finishing is all about prep and application. When in doubt , thinned lighter coats. If using rattle cans you can get a product at the auto stores called no blush. If you see your finish is blushing , you can hit it with the no blush 24 hrs after to stop spraying. Often a simple hair dryer can help to get the moisture out. Don't over heat the finish but warm air will help.
In warm dryer weather you can use less thinner. Think of it this way , in warmer weather , the moisture can get out easier , if the RH is high you may want to add some thinner . The retarder will let the finish flow and settle the thinner will allow a faster tack off as the volatiles come off faster and let the solids.

[Kevin Sjostrand]

Bob, the Rockler HVLP unit works just fine. It is not fancy, but puts down a nice coat of nitro with little overspray and you don't have to worry about moisture in the system....an issue to deal with when using an air compressor and spray gun.
For $100 I am pleased. I sprayed two guitars with it so far and I've saved alot of material....alot more getting on the guitar and not on the walls and floor of my spray booth. If you are going to do a few guitars, I'd recommend this system, or a better one if you can afford it.

Kevin

[watergunn]

I have used the Rockler unit on the last eight builds. Love it completely.

Went from using eight or nine cans of aerosol lacquer to one quart only.

Huge savings dollar wise. Paid for itself almost immediately.

I am by no means a professional finisher. But the results are amazing.

I attached a couple of pics.

Not the best camera work but the finish is unbelievable.

[naccoachbob]

Much obliged for the info everyone.
I took a picture of the spray gun that I bought a while back. Would appreciate comments on whether you think it will be good for lacquer spraying. It's HVLP.
It has, I believe, a 1mm nozzle. I was talking with an auto body sprayer about doing guitars, and he had his vendor drop it off at his shop. He seems to think it would be ok. Originally I got it for the electric that I was building, but ended up spraying with rattle cans.



The gunk you see at the bottom of the handle is residue from something taped on it. This gun has never been used.
Thanks,
Bob

[B. Howard]

Bob,
What brand is it? Looks sort of like a SATA and they are excellent guns. The 1mm tip should be close but may want a bit of extra reducer to get good atomization depending on what brand lacquer you decide to use.. I shoot a high solids nitro with a 1.4mm tip, no reducers, with great flow from my Devilbiss SRI. I have done a lot of work with disposable guns from Harbor Freight as well, so while good equipment makes the job easier as long as you get it set up right and match your RTS mix to what the gun likes and the environment you will be able to get good results. The regulator at the gun is a very good thing as well. Wouldn't shoot without one because that is where the pressure matters, at the gun. If you plan on any water based coatings make sure the gun is capable of it, some are not.