[QUOTE=Scott Shepherd;The whole "thinning" issue, what to thin with, and more importantly, how much to use has confused me for years.
Sparying latex throug a HVLP or a conventional siphon gun is not the best method. An airless is used for latex, and thinning is moderate, if at all. I've sprayed latex for years using siphon guns, but my application is for the sign industry and not walls and doors. And those that recommend Floetrol as a thinner are wrong. It is not a reducer it's an extender. Added to latex enamel for example, it reduces brush drag and allows the the brush strokes to even. But if your spraying latex through a siphon gun, you'll have to water the paint by 50-60% and you'll need several coats. It can change colors on you, too.
"I bought an airbrush several years ago and I fought that thing from day one. To this day, I know I have tried 4 or 5 different paints and I have yet to get the thing to spray properly (once again, illustrating I honestly don't understand this world of spraying)."
Paints for an air brush need to be as thin as ink and is usually used for art work.
"I have two things, (and by calling them things, it shows my technical knowledge), one is a gun that hooks to a compressor (normal compressor) and one that is an HVLP unit. I have painted a fair amount of latex and oil paints through the HVLP unit, but it's always been on home related stuff, so the finish doesn't have to be super slick."
A HVLP reduces overspray by about 90-95% and allows you to use more product through the tip. Again, not really good for latex paints, although small projects are about the only thing I'll use the gun on for satisfactory results. Spraying a vertical door with watered down latex is not good idea.
"Now, fast forward, I'm painting some sign blanks with both the HVLP and the other gun (tried both), and I can't seem to get a super slick surface. I had a sample someone did, and I put my next to it and the color is the same, but their blank (painted acrylic), looks like glass. Mine looks like it has the texture of an orange peel. It's fine for what I have been doing, but I sure would like to know if I need to get a different gun or what. I can't thin the paint with water, as it changes the color, which I can't have."
If I am painting sign blanks, either acrylic or metal, and I have to use oil or latex, I'll undercoat them with Bin pigmented shellac. You'll need several light coats because the shellac just sits on the blank because of the non porous surface. Bin is an excellent undercoat and provides a tooth for the paint. If I have a choice, I'll use lacquer or a professiona product call Matthews polyurethane,( sold only at sign supply companies). Orange peel is caused by too much pressue and or heavy material. You can get a glass finish using a HVLP, but the prep is the key and perhaps several coats and hand sanding in between.
"I also can't use oil based as I'm told the carrier for the paint is something that will crack or craze the acrylic"
Not sure what you mean, but alkyd products don't harm the surface of acrylic.
" Anyone got any tips to get me out of the "house painter quality" mode and more into the "automotive finish quality" with latex paint and being able to spray it?"
You will have to experiment with spray tips and material if you continue to water down latex through a conventionl or HVLP gun.
As I said, spraying sign blanks should be done with lacquer or a polyeurathane with an accelorator for top quality results.
If you would like to investigate the poly products, give me a jingle and I'll put you in touch with someone who can find a dealer for you.
Phil