I had this written up some time ago, but then just did not hit the post button.
I did not want to contradict Justin and though someone else would fill you in.
Just found it for you while looking for another file and....better late than never.
So are you still interested in painting, MDC?
This is what I had:
MDCmotorsports said:
Looking to get into painting cars and such.
Need to know the following:
-Basic technique
-Do they have "premixed" ready to shoot paints?
-What does hardner, catalyst, reducer, and thinner do?
-Is it nessecary (sp?) to shoot clear afterwards?
-What is the rule on paint... something like you can't shoot laqueer over varnish or something like that?
-What grit do you start out with. When do you wetsand? What grit then?
-HOW IN THE CRAP do you get right up to the windows?
Basic technique of spraying is to not stop the gun while shooting with material still being applied. Fade out each stroke by tilting the gun before and after so that it will blend in. Overlapping patterns vary with material.
Hardener is catalyst. Reducer usually refers to urethane paint that has a hardener in it. Thinner usually refers to lacquer paints in which there is no catalyst in the paint.
You
can not buy premixed paint. Paints, primers, and clears that use a catalyst will have what is called a pot life. A pot life is the span of time from when you mix the materials until they are hardened, unusable, and no longer sprayable.
You can't have premixed ready to shoot paint with a catalyst because the catalyst will harden the paint. Paints and other such materials harden in two ways:
1) drying from the solvents evaporating
or
2) a chemical reaction taking place when materials are mixed
Clear's purpose is to give a non porous finish. Clear protects the much softer and thinner film of paint, and it also blocks UV rays so that the paint does not fade. The paint you see on cars do have that system of paint in which clear is required.
Some painting system's don't require clear. Those are called single stage. They harden with a non porous finish and are durable paints that don't need the protection of finishing clears.
My rule of paint is to get off any crap that may have been sprayed by other people if I can't determine what it is. I don't build on crap. I build on my own foundations or the foundations from the factory. I think you are referring to lifting. I am not an old schooler so I am not in love with lacquers. I use urethane and airbrush colors. I have never had lift. I also use thinner a lot with urethane paint instead of reducer--never a problem so far. On a big car, thinner will dry too fast though and on that I would use reducer.
I try to limit myself to certain brands. Using too many brands puts one in an unfamiliar situation. Try to get familiar with one or two brands and try to stick with that.
You can start with many different grit because there may be many different problems procedures. If your surface and the body of the part is good, you need to determine if you are going to use primer or just paint it (some rare occasions, you can just paint without sealer/primer).
Some primers can cover over 80 grit sanded surfaces.
Some primer sealers need finer surfaces.
Primers that harden by evaporation (lacquer primers) will require finer sanded surfaces than ones that harden. Evaporation shrinks and so the material (primer) will shrink its coverage and filling properties as well.
320 grit is usually what works well before priming in the urethane system of painting.
Wetsanding: that is one way of sanding. Paper does not load with wet sanding so I wet sand whenever I can. It also keeps dust from going to your precious lungs since the dust stays in the water. I use soapy water to help the paper not load.
Masking--and masking well--is how you determine where the paint will go and where it will not.
SANDPAPER USE:
Before bodywork or applying filler: rough as you can: 40-80 grit
After bodywork filler—if fill primer will be the next step: 100-220
After fill primer is applied 320
Before sealers (if going that route): 320
Before metallics or basecoat for candies 500-600
Before basecoats that are not low pigment 400-500
Reclearing a job less then a week old: 600-800
Fixing dust particles in paint before coats or clearing: 1000
Wetsanding finished clear before polishing: 1500-2000 (I do the 2000 route).
Grits that are higher than 1000 are never to be used for sanding before spraying—unless it is to reclear a fresh clear coat. The only time you would ever use anything finer than 1000 is to fix dust particles between paint applications or as a step in polishing.
Sanding with too fine a grit does not help adhesion. You need to have different layers “bite” into each other.
When I lay clear, I lay it on. I can cover fine sand tracks. Some that like to use thinners with clears won’t be able to do things as I prefer. My system works flawless for me. Using thinners will make films not only shirk more, but not cover. (I am talking about clears and primers.)
