HVLP spraying

[Travis Porter]

Based on DavidF's and SteveD's comments on spraying, I have broken down and bought a Porter Cable PSH1 gravity fed conversion HVLP spray gun and want to use it to finish a toy box (once I finish the construction).

The directions/manual for the gun is the pits. I want to spray water based as I am a bit scared to do anything oil based without a spray booth, so any suggestions on what to beware of, what not to do, etc?

I am going to practice a bit before doing a piece of furniture, etc. but this is definitively going to be different for me. I expect I will use an oil based stain on the piece wiping it on by hand and will probably seal it with a coat of dewaxed shellac.

This will also be one of my first attempts with shellac. I suspect I will need to sand the shellac with 400 grit wet/dry paper. Do I need to use a lubricant, or anything before I topcoat? Speaking of which, what should I topcoat with? Water based poly maybe? Do I need to thin the poly to get it to work? I have been reading about Target USL which seems to be the best out there, but no experience. Will the standard needle work or do I need to get a larger one?

Any and all suggestions comments would be appreciated.

 

[Steve D]

Travis,

Cardboard boxes make for great practice, spray them inside & out, flats & verticles. You've got the goods, forget wiping stain, spray dye. I use the Target/Emtech USL for lacquer and have also used Target oxford hybrid varnish (poly). Shellac as a sealer would be a good move if you mix oil stain and water finish but not needed if you use dye with water or alcohol as the base. There isn't a need to sand the shellac sealer if you go that route. I always spray at least 3 coats before sanding to make sure there is sufficient build. On a typical finish I will spray 3-4 coats, sand with 300 grit and spray 1-2 topcoats. If you are planning to rub out the finish (lacquer) you may want to build more. 3-4 coats, sand, 3-4 coats, sand, 1 coat. Let it cure for several days and then rub out. Emtech can recoat in 30 minutes so you can spray an entire schedule in a day. If you spray the dye, wait overnight to topcoat. Let me know if you want more details on the dye.

 

[woodguy1975]

Standard needle works fine. I use the same needle for spraying all my finishes with my HVLP system. The key is setting up the fluid and air controls. You want the fluid control to where you are fully wetting the surface but not puddling. Once the fluid control is right you adjust the air to where you orange peel and then increase by 1 psi. Once your controls are set you can leave it for the most part and thin everything to the same viscosity.

Practicing on a carboard box is a good idea. The key for spraying boxes is keep your air down to a min. Too much air and you'll have a very rough surface due to overspray. You want just enough air to avoid orange peel and no more.

Good Luck,

John

 

[Travis Porter]

Yep, you started the dye thing with me, and I bought some transtint when Woodcraft had their 10 percent off sale. That stuff is EXPENSIVE. So, water or alcohol, and what mix ratio? Would you spray it as well. Tomorrow night, I expect I will be spraying some cardboard.

 

[Steve D]

Travis,

It is expensive but highly concentrated (wear gloves DAMHIKT) and it goes a loooooooong way. I have always used water, but if you are in a hurry or working with a wood type that grain raises severely alcohol is great too. Mix ratio is up to you but measure and record what you do in case you comer up short and need to mix more DAMHIKT. I use empty gatorade containers becaue they have a wide wouth and are easy to pour out of.

You can also play around with it and add it directly to your finish to use as a toner if you need to take care of Sapwood (the hat thing kind of freaked me out, i'd keep the toner gun loaded just in case :lol: )

 

[Travis Porter]

That picture was pretty scary, but after living in Durham myself for many years I have come to realize it is not abnormal there. If you didn't know it, that is why all the institutions are up the road in Butner.:lol:

 

[Steve D]

That explains it...:lol:

 

[michaelgarner]

Hey travis,
This is a great website I go to to get info on finishing, I am the classic take-forever-has-to-be-perfect-construction woodworker, I used to just throw anything on there to get it done. I use my HVLP now and love it
Be blessed
http://www.thewoodshop.20m.com/finishing.htm#maloof

 

[Travis Porter]

Thanks, it is new to me and I will check it out.

 

[Keith]

Don't forget to strain your dye!!!

 

[Travis Porter]

YOU HAVE TO STRAIN THE DYE??? Those itty bitty bottles of Transtint need to be strained?

 

[Steve D]

If so, that is new to me. I've never stained liquid Transtint in all of the spraying I have done. I do strain the finish though. There is also a Transfast powder dye, that might be a good idea to strain it in case there are clumps.

 

[Keith]

I buy dye in powder form and after you mix it you should strain it. Powder can be mixed with different mediums other than liquid.

 

[DavidF]

When I was at at the cardboard box stage I found it almost impossible to see any orange peel. When I then tried a piece of wood, I could see it, so maybe also practise on some ply or MDF? Another thing I found and was told my the wagner tech people was to get no further away than 2-3" when sparaying WB because the finish can partially dry before hitting the surface, this gives a rough surface feel.

 

[Steve D]

David,

2-3" sounds awfully close, I can't imagine that much of a fan spread can be accomplished at that range. I have always been told 6-8" FWIW. :eusa_thin

 

[DavidF]

I know, that's what I thought, but he was adament, and I have since read that somewhere eles too. He said that 5" was max for WB.

 

[Steve D]

I'll have to experiement with that. I've never sprayed that close in the past. I have always found that I get a rough surface on my build coats but I attribute that to grain raising. I usually spray 3-4 coats, sand level and spray a final coat. The final coat has always felt smooth to me.

In my experience, solvent based finishes seem to dry faster that WB, what distance do they recommend for nitro based lacquer?

 

[DavidF]

In my experience, solvent based finishes seem to dry faster that WB, what distance do they recommend for nitro based lacquer?

As I was only interested in WB, other finishes didn't come up.