Try my hand at spraying some enamel for a drill press rebuild

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makeparts

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I've looked thru a lot of threads... I think I see that folks prefer brushing over spraying enamels, due in part to the longer drying times thinned enamel takes to dry. Planning to tape up all the castings and sheet metal, prepping and spray it with an airbrush, as I'd like to try this as an experiment, and I have the equipment available to me.

very close by is a Sherwin-Williams paint store that is trying to match an early 40's Craftsman dark machine grey, in their metal compatible series of enamels. Their recommended thinner for this paint is mineral spirits.

Yesterday after mixing, when it was wet on the sample swatch, it was too dark. A good color match I thought, but too dark. Today should be a good test, if it has dried.

One of the employees mentioned that there are 2 options:
1) they can try to lighten the paint with a white, but that risks changing the color
2) Using their technolgy driven paint matching system,they can ALSO make the paint lighter such that the shade is maintained, but can be lighter or darker, and adjust the formula accordingly, before mixing in the dyes/colorants.
so we have some options...

I've read that lacquers tend to dry quickly, and something like penetrol is needed to retard drying, so the spraying device (airbrush, spray guns etc.) doesn't get clogged with dry paint.

Also read that thinned enamels take forever to dry, so using something like Japan Drier or Linseed oil helps with the curing process (VOC evaporation and then polymerization).

So I guess the questions I'm hoping to get discussed/answered if possible are:
1) if the oil based enamel is thinned with mineral spirits (try 1:1 first), will that change the color, make it lighter, or just thin it?
2) do the drying agents above make sense with enamel? if so, do they bring drying/hardening times down to acceptable levels?
3) would a cool water bath a day after painting help with curing as well?
 
Im FAR from a professional painter, so take my advice as so.
The most I've ever thinned paint was 10% thinners. I use a high volume low pressure gun with different nozzles to handle the different viscosities. (nozzle picked by guess) I don't find it takes any longer for a sprayed finish to dry than a brushed one.
In the cabinet shop I hand rub varnish thinned with about 30% mineral spirits, It dries very quickly, muck faster than brushed on varnish, probably due to the thin coat.
I've heard of Japan Drier but have never used it, linseed oil dries very slowly, so can't see it helping and would be concerned its colour would affect the paint colour.
There are hardeners available for enamel paints, I buy one from Napa, It apparently converts their Industrial enamel to a urethane. You add 10% hardener, the paint skins in about an hour and is hard overnight. I've used other ones that act faster.

Greg
 
f350ca said:
Im FAR from a professional painter, so take my advice as so.
The most I've ever thinned paint was 10% thinners. I use a high volume low pressure gun with different nozzles to handle the different viscosities. (nozzle picked by guess) I don't find it takes any longer for a sprayed finish to dry than a brushed one.
In the cabinet shop I hand rub varnish thinned with about 30% mineral spirits, It dries very quickly, muck faster than brushed on varnish, probably due to the thin coat.
I've heard of Japan Drier but have never used it, linseed oil dries very slowly, so can't see it helping and would be concerned its colour would affect the paint colour.
There are hardeners available for enamel paints, I buy one from Napa, It apparently converts their Industrial enamel to a urethane. You add 10% hardener, the paint skins in about an hour and is hard overnight. I've used other ones that act faster.

Greg
Click to expand...
hey Greg thanks for the info. do you find thinning the paint at 10% (which is 1 part thinner, 9 parts paint?) allows the color to remain consistent with the unthinned paint?

I'll share what the Sherwin-Williams folks offer as info here when I get a chance.
 
The thinner simply evaporates so I expect it has no effect on the paints pigments. Or so I think. Yes 9 parts paint 1 part thinner.

Greg
 
I've used several different brands of oil based enamel for machines, mainly because of the cost compared to automotive paints. Typically oil base enamel no matter what brand will take about 6-8 hours or maybe more to dry right from the can. I have had the best luck with adding the gloss hardner and japan drier to speed up drying time, and typically you can remove the tape after an hour. The japan drier is the color of red wine, so it will slightly darken light colors, not noticeable on dark colors. It only takes 2 oz. to the gallon, so it's not much. As far as thinning will depend on your spray gun. I add only what it takes to get a good flow. You will have to experiment with a little at a time to figure it out.
 
I don't think Thinners will effect color. The Thinner is part of the carrier and is expected to fully evaporate after it has done it's job leaving the pigment behind.
 
In my experience thinners have no effect on color or hue. Viscosity and opacity but not color. I've had great luck getting great durable paint jobs using inexpensive harbor freight HPLV guns and even rust-Oleum from the box stores. I've used some pretty high dollar paint guns over the years and was pleasantly surprised with the results I got with the HF cheapo guns. Others post simular reviews of some of these low cost guns. I base it on weather for the most part. Out of the can un-thinned in colder temps enamel may seem like it will never dry/harden and even in warmer weather it can take days and you can still dent it with a finger nail. I started thinning with either Acetone or Naptha. For colder weather light coats with a bit heaver final coat so it can level. Do a little research on thinning. You'll find 2 parts thinner to 3 parts paint work pretty well. Less thinner or more, even up to 50% and you will get very acceptable results. Acetone will dry faster than Naptha. Regular thinner (which I wouldn't recommend) comes in third. Reducing or increasing the amount of thinner is easier than messing with different types of thinners. Try a couple coats and test drying times and coverage on a test piece and adjust accordingly. They even have throw away containers for the HF HPLV guns which make clean up a snap, just chuck the used container and run a little thinner through the gun to clean it, store it in a zip lock and it's be ready next time you need to use it. Good luck.
 
Thinner will not change color unless used to excess. Too much thinner and colorants will sometime float causing a mottled coloration. My preference is naphtha , no more than 25%. Warm temps , 70-80 F. Multiple thin coats, keeps down runs and sags. Allow to tack, then remove tape to keep from pealing new paint. Maintain temp till dry. DON'T RUSH IT.
Dave
 
The only time reducer or thinner SHOULD change color/shade is if you are using metallic paint with flake in them. The slower it dries, the more the flake gets buried and the darker it gets. Faster lets the flake sit on top and makes it appear lighter. Mike
 
I've painted several machines and I found automotive acrylic enamel with activator/ hardener works the best. ( If its good for your car its good for your machine).Depending on the ambient temperature and humidity, use the appropriate thinner. In High temps around 80F and above use a fast thinner, in lower temps 60 - 80F use a slow thinner. The thinner speed determines flash time of the paint. Go to a auto paint supplier they will point you in the right direction. You'll also be able to pick from thousands of available colors, that they can match any color
 
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