<BR>
Re: Primers

After it is all said and done, all primers are not created equally. Picking your primer is just, if not more so, important than picking your paint. It becomes your base, that all your other paint is attached to. Just like building a bridge, if you build a weak foundation, things could crumble.

The primary primer rule
Primers are not waterproof. I'll repeat that again. Primers are not waterproof. If you have a work-in-progress, do not expect to cover your bodywork up with a little primer, while you drive your rig around in the rain.

There is one exception to this rule and I'll explain that below.

1K primers
These are your one-part primers usually found in rattle cans. Normally enamel or lacquer based that are air-dried. They were used for years but are old technology. Positively not waterproof. About the only time I use this stuff anymore is as a temporary covering. In other words, if I use it, I expect to remove it in the near future.

If you insist on using this stuff, expect to cover it up with a sealer, before you apply any of the newer paints.

Self-etch primers
This primer can be found as a 2-part primer or in a rattle can. It is acid based and etches the metal. This provides an extra measure of attachment security. I still use this stuff although epoxy primer is my normal preference. By the way, self-etch is not designed to be used over the top of other primers or paint and can cause compatibility (i.e lifting, wrinking, etc.) issues.

2K primers
This normally refers to a 2-part urethane high-build primer. You mix it when you need it and apply with a spray gun. As far as I'm concerned, this stuff is the only way to go when it comes time to flatten out the high and low spots in your bodywork. Apply 2 or 3 coats, blocksand, apply another 2 or 3 coats, and repeat until you're happy. Besides having a high-build factor, the shrinkage factor is very low. That means those 80 grit sanding marks won't show up when the primer dries.

Epoxy primers
This stuff is great. Seals out water and seals in micro-rust. Compatible with just about everything. Can be used as a sealer (a protective coat between different types of paint). I use it under any filler (AKA bondo) work I do. Apparently there are types that are not designed for DTM (direct to metal) application. Consult with your paint vendor when you are buying.

 

<BR>
Re: Saving hardener

Hardener works many wonders. It makes your paint or clearcoat hard and it gives it that high gloss that we all love. Wonderful stuff but it does have have a downside (besides the isocyanates that are associated with it).

The downside is that hardener gets hard. What, you say, I thought that was one of the wonders of hardener? Well, it not when the hardener sets up in it's own container.

Once you crack the seal on a can of hardener, it is suppose to be used. All of it. It was never designed to set on someones garage shelf in a half filled can. Once the hardener is exposed to air and moisture, it starts setting up. First it will change into something as thick as sprup. Give it a little more time, and it will change into a solid lump. By the way, this is reason Por-15 paint has to be used in one session. Por-15 contains a hardening agent.

You can stop the process by sealing the hardener from air. The best way I have found to do is is to shoot a little gas from my mig welding unit, into the container of hardener. Although straight argon would probably be best (because it is inert), I have found that straight CO2 also works great.

For those without a gas mig unit, you might try contacting your local paint supplier and ask for "Blow Ox". It is a can (similiar to a rattle can) of inert gas that is used just like I described. I don't have the correct spelling of this product but just ask for "Blow Ox."

 

<BR>
Re: HVLP (high volume low pressure) paint guns

These are the latest types of spray guns and in some locations, the only legal spray gun you can use.

An older conventional gun required an high inlet (where the air line attaches to the gun) pressure. There would be slight loss of air pressure and the paint would come out the tip at a slightly lower pressure than the inlet. For example, you might set your gun at 65 p.s.i. and the paint would be sprayed at 55 p.s.i.

The HVLP gun works differently. You might have 55 p.s.i. at the inlet but the paint leaves the tip at 10 p.s.i. To do this, the gun requires a large volume of air. Thus the name, high volume, low pressure.

The advantages are less waste, less overspray, and less pollutants in the air. This is why locations that are sensitive about air quality require a HVLP gun.

It can get confusing the first time you use a HVLP. Then you look at a HVLP gun, it is usually marked at the tip with something like "10 p.s.i. max". What they are talking about is 10 p.s.i. "at the tip", not "at the inlet". If you try to set the gun to an inlet pressure of 10 p.s.i., it will not work.

To muddy the water even more, you can not measure 'at the tip' pressure without a special measuring device. Although they are available, I don't anyone that has one. The best way to find out how the inlet and tip pressures correspond are to contact the maker of your gun. By doing that, I found my Sharpe Platinum requires 55 p.s.i inlet to produce 10 p.s.i. tip pressure. A no-name HVLP I have requires 43 p.s.i. inlet for a 10 p.s.i. tip pressure.

A Warning
Air volume (not pressure) is measured in c.f.m (cubic feet per minute). HVLP guns require a lot of volume. Most of your cheaper air compressors will not produce the volume of air you need. My Sharpe Platinum LV is one of the lowest in the industry but still requires 7.5 c.f.m. It's not uncommon for a HVLP gun to require 11 - 14 c.f.m. Check the stats on your compressor and gun before you start painting your rig.

 

<CR>
Re: Is my air compressor capable of doing a total repaint?

First off, lets start with a couple of definitions.

<UL>
psi -- Pounds per square inch (Pressure of the air)
cfm - Cubic feet per minute (Amount or volume of air)
</UL>

When most people go out and buy an air compressor, they end up focusing on horsepower and psi. "Look at that. It has a 5 horse engine and will make 125 psi and I can run it on 120 volts."

While the facts you are considering may look impressive, they are not what you should be concerned about. Horsepower, voltage, and psi have little to do with the ability to use air tools or a modern HVLP paint gun. The true factor to be concerned about is:

<CENTER>
<H2>
CFM
</H2>
</CENTER>

Lets take my compressor for example. These are the stats:

[UL]
5 horsepower
150 psi maximum
18.5 cfm @ 100 psi
[/UL]

This baby is about 6' tall and has 3 oil-filled cylinders. It will run just about any HVLP paint gun or air tool I need. All day long !! My problem is, this was the 4th air compressor I bought. Each previous compressor was just too small. It wasn't until this one that I finally had one that was big enough.

Your small compressors will be rated something like 5 CFM @ 80 psi. These are the type you find in your typical Sears and Home Depot stores. Great for pumping up a tire or blowing the dust off your workbench but almost useless for running air tools or HVLP paint guns. This is the main reason your compressor won't run that impact wrench you have. Your compressor doesn't have the cfm required to run the tool for any length of time.

The bottom line
Most HVLP paint gun require 7.5 - 14 cfm @ about 55 psi. With that information, look for the stats on your compressor and see if it big enough. If it's not, then most likely you can't do a complete repaint. Your air compressor won't be able to keep up.

 

<br>
RE: Prepping your work

It's been said, prep is 99% of the work involved in a paint job. I believe that. This short section will deal with the cleaning prep you should be doing before you even touch your rig with a sander. These principals apply to both a total repaint and for spot repair. You will need the following items:
<ul>
Bucket of hot water
'Dawn' dishwashing soap
Scrub brush, rags, toothbrushes, & etc.
Grease and wax remover
Spray bottle
Paper towels
</ul>
Fisheyes, pits, lifting, popping, & swelling are just some of the problems that can occur because of improper or incomplete surface preparation. Contamination such as dirt, tar, and silicone will ruin a otherwise perfectly good paint job.

First off, get a bucket of hot water and give it a good squirt of 'Dawn' dishwashing soap. My wife swears by Dawn as a great grease remover and I'm a believer. Others may work as well but since I've had good luck with Dawn, I'll stay with it.

Now take your scrub brush and scrub (and I mean scrub) your work area. You aren't going to a car show. You are going to a paint booth so don't be afraid to attack the area. Rinse the area well with water. I have soft water in my area but for those in hard water areas, some go as far as buying distilled water for the final rinse. Allow it to dry completely.

Put some wax and degreaser in a spray bottle. Spray it over the work area and wipe it off with paper towls. The idea is to float any grease and then pick it up with the towels. Rubbing the degreaser on and wiping it off will merely smear the grease around. Spray on & wipe off. It's the best way.

Always prep before you start sanding. Sanding over grease will only force it into the sanding marks.

I figure on using a gallon of grease and wax remover for a total repaint, since I degrease several times during the paint process.

Once I have my area prepped, I only touch it while wearing rubber gloves.

Grease and contaminate can come from any number of sources. They include, but aren't limited to, your hands, air tools, silicone based detailing/cleaning compounds.

 

If I paint with an enamel, how much do I have to thin the paint with? jim

 

What brand (Dupont, PPG, etc.) are you using?

 

I am using PGG....jim

 

PPG's MAE Acrylic Enamel uses the following reducers:
<ul>
MR185 - Fast
MR186 - Medium
MR187 - Slow
MR188 - Very slow
</ul>
It calls for a mixing ratio of:
<ul>
4:1 (MAE:MR)
</ul>
The flashtime is:
<ul>
5-10 minutes @ 70 degrees
</ul>

 

Thanks 4starcstms I have a 1979 Cougar XR-7 and a 1986 Ford F-250 Super-Cab 4x4 to paint. I'm fixing the rust on the '86 and the Cougar is ready for the final sanding and priming, so your advise really helped. Again Thanks

 

Is there a rule of thumb for hardeners?
I am going to use HOK urethane enamel for my painting. Which hardener should I use fast slow etc.? Is it only a mater of temp?

 

prep question??
I am in the process of sanding the old paint down to bare metal to prime and have painted. I have been using 100 grit sandpaper on the original factory paint. Am I using to heavy of a grit. and is'nt this paint lead based

 

When I strip a rig, I use 32 grit, on a DA sander, to strip all the paint off. Then I resand with 80 grit. Others I have talked to use 100 grit for the entire job. I guess it just depends on what you were taught, since in the end results, I can't see any difference. Just be aware though, if you see sparks during your sanding, that means you are removing metal, not paint.

Not sure if it is lead based but you can be sure that no sanding dust is good for you. Wear protective gear.

 

daimon1054:

Yes depends on the Temp, the hotter the temp the slower you want it to harden, the colder, the faster. And by cold I mean no colder than say 68-70

 

Not sure on the lead either. Sorry. I too would use 32 grit and finish the metal off with 80 before using some sort of epoxy primer or some of the metal etching primer from eastwoodco.