HVLP for finishing.

[Ed_McDonnell]

Anyone using HVLP (turbine driven, not a compressor conversion) for applying finishes to turnings? I've been doing some research just in case I win the lotto or something and the more I research the more confused I become.

2 Stage, 3 Stage, 4 Stage??? I think I understand that more stages means higher air volumes (and generally higher fluid volumes), but how much do you really need? This would be exclusively for finishing turnings in a non-production environment. There is zero possibility that I will ever attempt to paint my house with the thing. I really want a super high quality finish and imagine that I would mostly be using lacquer, but occassionally oil / water based poly.

Bleeder or Non-Bleeder. This one really has me confused???????????????

Gravity feed vs pressure pot / cup. Why would you ever want to use gravity feed? I've been playing around with a cheap (I stress CHEAP) Horrible Freight gravity feed HVLP spray gun that works off my shop compressor. It does ok, but just ok (well, maybe a notch below OK).

What kid of spray pattern works best on turnings (things like bowls and vases) and how important is it to be able to vary the spray pattern while working on a piece?

I've got more questions, but I'll stop now and see what kind of a discussion develops.

Ed

 

[Mark Mandell]

Hi Ed.

First a few basic things. The stages of the turbine guns are actually units in the fan block and determine how much air the thing will push. Remember, the basic concept here is that you've got a spray gun hooked up to the end of a vacuum cleaner exhaust hose. The more air flow you have, the better the gun will atomize the heavier finishes into smaller and smaller droplets. For finishing turniings with lacquer, you don't need a 5-stage air monster.

"Bleeder" guns continuously allow air to "bleed" through them, even when they're not being held, they are noisey which just adds to the racket the turbine makes. I had a bleeder gun on my 3-stage Fuji outfit. I did not like it and sold the whole outfit and went with conversion guns for better results with evaporative finishes.

Now, for spray finishing turnings, I would suggest you consider an HVLP mini-gun with a gravity feed. I got a CAT Tech Jr. Minijet for x-mas, and have used it for spraying turnings as well as seal coating (shellac) of flatwork. Its atomization is truly great with a very accurate and even pattern, yet it's light and maneuverable and it will run quite well on 20psi with 4 CFM for shellac and 20% thinned waterbornes, so even smallish compressors will run it nicely. At $145 it comes with three air cap/needle sets that will allow you to work thin clears up to some latexes and comes with cups for both solvent and waterborne finishes. It is far far better than the touch-up siphon gun I got for turnings. And, IMO, much better than a "Critter" gun which I know many folks use for lacquering small stuff.

The turbine guns are great for waterborne finishes because the guns and airflow get quite warm [so warm they have to insulate the handles or you couldn't hold them] and help to dry the finish. I did have some issues with orange-peel with my Fuji on shellac and lacquer until I starting adding retarder. I also use a Walcom FZ SP conversion gun with pressure pot for furniture, but that's way overkill for turnings although it will lay down waterborne and evap lacquer like glass right off the gun. Make no mistake, there are some fine turbine units out there like the new Fuji Q, but you're looking at $700 to 1K depending on where you buy. The new Apollo Atomiser gun is really great, I hear, and it also allows you to use a top cup, bottom cup or pressure pot all with the same gun. However, just the gun is $400+ so that may not be an option for you.

Hope this helps

PS Here's a link to the place I bought mine. http://www.spraygunworld.com/products/CAT/CATMiniJet.htm

I added a mini-regulator to the gun. You can get them from HF for under $10. It allows micro-fine adjustments to the airflow to maximize the HVLP and minimize the overspray. Also saves going back to the compressor and phutzing with the big regulator.

 

[KurtB]

Hvlp

Ed,
I agree with Mark, do not buy a bleeder type. They blow air constantly, which kicks up dust in the shop, or dries the previously shot lacquer too quickly. The biggest advantage of HVLP is that it doesn't shoot overspray everywhere. You're right, though, that 2, 3, or four stage aren't necessary for shooting turnings. The simpler, the better.🙂
Kurt

 

[Ed_McDonnell]

Thanks Mark, that helped a lot. What is the reason for the "bleeder" design. In my research I've seen strong preferences for one or the other expressed, but no real discussion of what the functional differences are. There must be some design logic for bleeder versus non-bleeder designs. I haven't found it yet though.

I've had orange peel problems when spraying shellac with my cheap HVLP gravity feed gun. I've been blaming the gun when maybe a little of the retarder you mention might help. I've seen references to retarder in finishing books I've been browsing through, but I haven't seen it in the woodworking stores, catalogs or home depot. Maybe I'm looking in the wrong place. Is that something I'm more likely to find in a paint store (assuming I can find a paint store these days)?

I'll check out the Cat TEch Jr. you recommended. $145 might not even require a winning lotto ticket. I was looking at the Apollo, Turbinaire and Accuspray systems and they sure look nice, but they aren't in the budget at the moment. I'm also not convinced that they are what I need to get the finish I'm looking for. I have a lot of work to do to improve my technique and learn the tricks of the trade. I just recently learned about stearated sandpaper and the problems it causes lacquer finishes. That's one of the things I like about this hobby. It seems you never run out of new things to learn.

Thanks for the reply.

Ed

 

[Ed_McDonnell]

Hi Kurt - Do you happen to know what the reason is behind the bleeder design? Somebody must think it adds some functionality or else makes the design less costly???? I'm sold on avoiding the bleeder, but I'm really curious about why anybody would want it or find it useful.

If you don't mind my asking, what system do you use for your spray finishes?

Thanks for the reply.

Ed

 

[KurtB]

Hvlp

Ed,
I had a Turbinaire system, and I really liked the job that it did. My shop is not small, but my finishing area is, and I wanted a turbine system to cut down the overspray. I read articles that said if you learned how to use a spray gun on a compressor, you probably wouldn't like a bleeder gun. I believe that the purpose was to eliminate any hot spots from starting and stopping the spray pattern, but if you learned on a compressor setup, you should already be used to the pattern of spraying past the object, and starting before the object to get an even pattern. The only advantage of the bleeder gun, as I saw it, was that you could blow the dust off the object without pulling the trigger; but you could turn the gun while hanging it up and kick up dust just as easily. I'm not entirely knowledgeable on this subject, but these are the things I came up with from using it on cabinets for 2 years. Hope this helps.
Kurt

 

[Jake Debski]

The bleeder gun was a cheap way out many years ago. A small compressor(running continuously, no tank), my dad had a DeVillbis, would only work with a gun that "bled" air, otherwise something would explode. Why they do it today is probably for the same reason(cost) it eliminates the need for a pressure switch to shut off the turbines or some other mechanism to allow the air to escape or recirculate.

 

[Mark Mandell]

Retarder

T I've seen references to retarder in finishing books I've been browsing through, but I haven't seen it in the woodworking stores, catalogs or home depot. Maybe I'm looking in the wrong place. Is that something I'm more likely to find in a paint store (assuming I can find a paint store these days)?

The easiest retarder for Shellac is pure gun turpentine (the REAL stuff]. Behlen Solar-Lux also does well by adding up to 10%, but I prefer the turps. Just a few drops in a cup of shellac will slow the alcohol evaporation and allow the film more time to flow out and level. You do want to watch it on vertical surfaces, however, or you'll get sags.

You should also work on your technique. Keep your gun as close to 90° to the receiving surface as you can and no more than 8" away from the surface. Orange peel is usually caused by the finish drying too much BEFORE it hits the surface.

As far as retarder for lacquer. You should inquire about that based upon the lacquer you use. Your lacquer supplier with have various option for fast to slow drying in different conditions.

I always start and stop my application stroke off the edge being sprayed, with either bleed or non-bleed gun. Otherwise you risk starving the edges for finish. True, with evaporative finishes you should double hit in both directions, but I still like the control of a non-bleeder better. As mentioned , it may just be my training.

mm

 

[4mikee]

Maybe this is useless information but here goes anyway. HVLP's are great...Many years ago I used the turbine units (still have one) for painting cabinets, trim and lacquers. I've used it to spray catalyzed(?) pigmented lacquer on the kitchen cabinets I built and I've spayed indoor cabinet refinishing jobs (cut the central unit and pilot light off). I've had the turbinaire and the Wagner professionals. Having given a bit of background I'm curious why you don't want a gravity feed that attaches to a compressor. I see the advantages of the turbine but I wouldn't drag mine out for the difference in quality. I've tried a couple of the gravity feeds but the Kobalt from Lowe's at $99 is a steal for the quality. It's sitting on top of a cabinet with thinned lacquer at ready and has been for several months. Easy to use. Just another two cents worth. Oh, if you want it to dry really fast add some MEK or a little lesser solvent instead of lacquer thinner.

 

[Ed_McDonnell]

Hi MIke - After all this discussion, I may be rethinking the HVLP conversion (gravity feed connected to shop compressor), but the reasons I initially didn't want one are:

- All the high quality HVLP guns I investigated wanted more air than my compressor can deliver. Following Marks links led me to some guns that may be able to work with the air I have available so this issue may go away.

- I've been using a cheap HF HVLP gravity feed gun with my compressor. Results with shellac have been underwhelming. Haven't even tried it with lacquer. I could probably be convinced that a HVLP gravity feed gun that costs more than $20 might perform better.

- My compressor is oil-lubed. Sure I coudl filter the air, but the clean air from a turbine was kind of appealing.

- Local weather conditions make condensation an issue when working with compressed air. Filters won't completely solve this problem. The warm low pressure air from a turbine sounded enticing. My shop isn't airconditioned and I don't have the nerve to ask the LOML if I can spray inside the air conditioned house.


Ed

 

[4mikee]

Actually Ed I don't filter and haven't had any noticeable problems. (I'm looking for the lightning bolt now.) I'm well pleased with mine but it's not the only only one out there as Mark has shown. I've got a HF on the shelf, it's good for something at only $9.99 but I'm not sure what.....The Kobalt unit doesn't take much air, I can look if you'd like or you can check it out online so your compressor may be less of a problem than you think. Be sure to wear a respirator (lightning...). Keep in mind Mark's unit may be a superior unit, I can't say. Lately I've found myself getting away from spraying and using wipe on poly and buffing. It would be interesting in knowing what some of the others routinely spray as I have only sprayed lacquer on mine. You mentioned earlier something about a pressure pot and painting, personally I would stick to other sprayers for that purpose.
Let us know how it works out.

Ed I just looked back at the post and I need to point out that I don't use my oil lube but my oiless for the spray gun. A cheap unit from HF (nail gun size) would probably drive it fine. A quality HVLP spray unit would be much more.
Later

 

[Mark Mandell]

Filters

Ed,

[No lightening here, Mike]

A coalescing filter is easy to use and cheap, so I recommend them. The pic shows the air "station" in my basement shop. It's a HF on sale for -$20 and does just fine. In the pic you may notice that I replaced the stock drain valve with a 1/4" ball valve. I did the same thing on my small compressor. Much better and easier to let the condensation out of both the filter and the tank. If you keep your compressor's tank clean and drained of condensate, your air will be fine. This is no less true of oilless units.


There are also in-line filters that you can buy with replaceable cartridges that will tie in right to the handle of your gun. Again not much $$

 

[4mikee]

That's good to hear Mark. I believe these are on sale in the lastest bi weekly sale paper. They're pretty cheap especially with the 15% coupon. I recently added a large tank oil compressor so I can sandblast (another expensive lesson). I like your copper lines, I mail pm you at some point if you don't mind when I'm ready to run some lines.
Thanks

 

[Mark Mandell]

That's good to hear Mark. I believe these are on sale in the lastest bi weekly sale paper. They're pretty cheap especially with the 15% coupon. I recently added a large tank oil compressor so I can sandblast (another expensive lesson). I like your copper lines, I mail pm you at some point if you don't mind when I'm ready to run some lines.
Thanks

Note from experience, Mike:

The unit consists of a casting on top and bottom with a "seemless" steel tube for the body. The castings are chrome plated but are definately NOT cast IRON. Therefore, it will be easy to crack if you over torque the pipe thread going into it. I had to get my first one replaced by HF when this happened on the install. I then used pipe "dope" [not teflon tape] the make the threaded connection and it has been fine for 5 years.

Note too that there are smaller and "standard" filters but not many with steel or other metal bodies. Many actually use polycarbonate [Lexan] bowls which are very strong and will show any build up of condensate or debris from the air stream, but will break down in the presence of synthetic compressor oil which you should definately use in any oil-lubed compressor.

Last note: Re the copper - 1/2" or 3/4" Type L only, lead-free silver-bearing solder only, cast copper or brass fittings whenever possible. Price of copper is about to the point where galvanized steel pipe may be worth the hassle to install.

 

[4mikee]

I certainly appreciate the heads up Mark. I look into it more in a week or so. I've got a compressor sitting under my shed that's supposed to be swapped out before I hook it up (came out of the box with issues). Thanks again.

 

[Ed_McDonnell]

Mark, Mike & Jake - Thanks for all the info.

Mark - A filter for the compressor is on my "list". Someday I might actually get down that far. If I decide to use the shop compressor with a conversion gun "that day" will be a lot sooner.

Mike - I've been using wipe-on poly for the majority of my turnings for the last couple of years. With nothing to compare to, it creates a really nice high gloss finish. BUT, put a wipe-on piece next to a well-done sprayed lacquer piece and the wipe-on poly just doesn't look as good to me. Something about a really well done sprayed lacquer finish that can't be duplicated with wipe-on poly. (not by me anyway)

Wipe-on poly is very easy on simple forms, but now that I've started adding carved elements and embellishments to my turnings (feet, ruffled rims, sunken inlays), the wipe-on is a lot harder to finish well.

I've also got some pieces I want to finish without any ambering. I've tried wiping on water based finishes and I just couldn't make it work. Just another reason I'm interested in moving to spray finishes.

Ed

 

[4mikee]

Ed if you makes you feel any better about the information I've shared I was struck by lightning and have been color blind since. Well, partially true I am color blind and if it turned them amber I'd never know, now i do. The lacquer is nice, handy and using wet paper sands to a soft feel. I too am getting into carving and sculpting and used poly on a couple of pieces of Spalted Sycamore blown down in Katrina. It did seem to darken it which may equate to Amber in my eyes. Thanks for that bit of info I'll remember that. Another note, I have started sandblasting after admiring Pacal Oudets work and finally got it down then I bleached it and it looked great, then I sprayed lacquer and it no longer has that real bleached look, darkened it to some extent.
Good thread.....

 

[Mark Mandell]

I've also got some pieces I want to finish without any ambering. I've tried wiping on water based finishes and I just couldn't make it work. Just another reason I'm interested in moving to spray finishes.

Okay, Ed,

Here are as few alternatives:

M.L. Campbell's "Krystal" lacquer comes very close to water white in a solvent-based lacquer. A solvent lacquer will give you the advantage of 100% burn-in on the prior coats so it can save you a lot of work leveling the film between coats.

That said, Target's "USL", Ultima Spray Lacquer, is an excellent acrylic lacquer with significant (not 100%) burn-in if handled properly. Preferred source is Jeff Jewitt through his websiite http://www.homesteadfinishing.com

If money is no object, Unaxol http://www.mobydicksupplies.com/index.html is great stuff, hard as nails, and water white I'm told.

Note as well that the waterborne lacquers are easily tintable in a rainbow of colors if you so choose. Again, Jeff Jewitt's "Trans Tint" pre-mixed dyes are the way to go here.

Have fun