Paint Problems

coyotechet · Aug 23, 2010

I am painting a SBL 10L. Removed all the old paint down to bare metal. Then I primered first with Sherman Williams Kem Kromik Metal Primer. It went on very nice and dried rock hard in 16 hours. I waited 37 hours before painting the top coat with Sherman Williams Industrial Urthane Alkyd Enamel. I used both a short tap trim roller and a Purdy China Bristle brush to apply the paint which was recommened by S/M factory. I painted the pan 18 days ago and the paint still has not dried. To touch yes it is dry but you can with your finger nail very easily scrape it off and roll it into a putty ball. It is VERY tacky and soft. Painting in the garage with over head doors opened. I have moved some of the parts to the basement shop area, which is air conditioned and some parts out side into the direct sun light. Still all the parts are not drying paint still VERY soft. Looks like I will have to remove all the paint from parts that I have painted. If so the bed is going to be one heck of a job removing the paint from all the webbing in the bed. Does any body have any ideas that might be helpful. I have taked to Sherman Williams people and they say that I applied the paint wrong and that it should be dry within 7 days. I have been going round and round with S/M but not getting any help. Right now I am not a very happy camper. Help. Thanks Chet

Rudd · Aug 23, 2010

sounds like it skinned over - paint too thick, either applied thickness or viscosity or both. Once it skins, you're kind of screwed, the surface doesn't allow much evaporation of solvents. High humidity makes this more prone to happen.

2 part epoxy paints don't do this. Some 1 part oil paints work better with a little (very little) Japan drier in them.

Joe Henderson · Aug 23, 2010

Just a thought. Before I stripped all that work I would bathe that thing in heat lamps for a while to try to speed up the process some. It couldn't hurt to try.

Good Luck,

jh

coyotechet · Aug 24, 2010

Rudd said:
sounds like it skinned over - paint too thick, either applied thickness or viscosity or both. Once it skins, you're kind of screwed, the surface doesn't allow much evaporation of solvents. High humidity makes this more prone to happen.

2 part epoxy paints don't do this. Some 1 part oil paints work better with a little (very little) Japan drier in them.

Rudd this sounds like exactly what is going on. The top of the paint is dry but right under the very thin outer shell the rest of the paint is still oiley. And now after 19 days it should start being hard. The pan is by far the worst. Yes two part epoxy is what I should have used. But the poeple at Sherman Williams told me I would be much better off if I used the Urethane Alkyd enamel. Because it was not as messy and dried very hard. Also I asked the poeple at S/M why the paint was so thick. And was told that using a brush I should apply it as is, it will smooth out before drying and look much better.
Rudd are you in the paint business if not maybe you should be because you should here some of the stories I am being told by the Sherman Williams People. Thanks Chet

reggie_obe · Aug 24, 2010

I'd try what JH suggested before trying to remove the paint. A couple of Halogen work lamps, positioned close to the parts should provide enough heat to help the paint cure.

paul39 · Aug 24, 2010

You might want to sand a couple of pieces of steel and put a very thin coat on one and a thicker one on the other.

Let them sit for the same time in the same conditions as the non-drying lathe parts. Keep notes. If they don't dry, the paint is bad and you have some evidence to argue with SW.

I agree to give the lathe some more time to dry with added heat or sunlight. Be careful with halogens, too close can burn the paint.

Keep testing the paint on the lathe by pressing a thumbnail into the paint to see if it is getting harder.

Paul

coyotechet · Aug 24, 2010

I had posted wanting help on removing the new undried paint. But will try the Halogen work lamps, for a couple of days before I do any more about removing the paint. The pan is a real mess dry on the outside oiley as heck under the dried outer shell. Close to 3 weeks one would think the paint should be fully cured S/M information says full cure 7days @ 6.0 mils thick wet, @ 77*F, to 110*F. Thanks Chet.

paul39 · Aug 24, 2010

One would think that after 3 weeks it would dry if it is going to.

For removing, if you can start the skin peeling with the tip of a knife, peel like peeling a peach. Then put the part in a shallow pan and scrub with a nail brush, vegetable brush, tooth brush, with the solvent that is recommended as a thinner. Rinse with clean thinner and let dry thoroughly. I would do a test patch or two to see how they dry.

Good luck, I'm sure this is a heart breaker for you. It would be for me.

When I bought my filthy, swarf filled, well worn, Heavy 10, I just disassembled, cleaned, lubricated, put it together, and used it.

I admire the beautiful restorations I see on this site, I don't have it in me to do it.

Paul

rbwillnj · Aug 24, 2010

Just for the record, I have used the Sherwin Wiliams Industrial Alkyd without any problems. It dried to the touch in a day, and hard in two to three days.

I did thin the as received paint with Xylene (the recommended solvent), and applied two thin coats with sanding in between. I also added a small amount of Penetrol to aid with leveling. I applied the paint with a very soft artist brush purchased at a local craft store.

coyotechet · Aug 24, 2010

rbwillnj said:
Just for the record, I have used the Sherwin Wiliams Industrial Alkyd without any problems. It dried to the touch in a day, and hard in two to three days.

I did thin the as received paint with Xylene (the recommended solvent), and applied two thin coats with sanding in between. I also added a small amount of Penetrol to aid with leveling. I applied the paint with a very soft artist brush purchased at a local craft store.

The paint I am using is Sherman Williams Industrial Urethane Alkyd enamel. Also what is Penetrol and where do you get it. Sounds like a good thing if it helps because this suff does need help in leveing area. I also use a small camel hair brush for the small parts. The one part that is not drying at all is the pan which was the first thing I painted. So far I have only painted 1 small part and it does look as if it might be drying. The humidity has been very high here for the past month. The parts that I have taken to the basement shop air conditioned do look like they may be drying after 15 days in the garage and 3 days in the basement shop. Thanks Chet

alg4884 · Aug 24, 2010

coyotechet said:
The paint I am using is Sherman Williams Industrial Urethane Alkyd enamel. Also what is Penetrol and where do you get it......

You had better check with Sherwin-Williams before you attempt using anything to thin your Urethane-Alkyd paint. It's chemistry makeup is different from regular Alkyd paint. The urethane component of the paint changes the way things are done.

I have used Benjamin-Moore's (M22) Urethane-Alkyd paint in the past. When I checked with with B-M regarding it's thinning, they advised me not to do it.... To use straight from the can for both brush and spray. Adding thinner apparently changes the properties of the paint.

alg4884

coyotechet · Aug 24, 2010

You had better check with Sherwin-Williams before you attempt using anything to thin your Urethane-Alkyd paint. It's chemistry makeup is different from regular Alkyd paint. The urethane component of the paint changes the way things are done.

Yes I was told the same thing . But was also at the same time told that I could use Mineral Spirits, R1K4, Xylene as a reducer or thinner. And the Product Information sheet put out by Sherman Williams says the same thing. When I put the paint on the pan and after a week of not drying I took the paint back to Sherman Williams and was told that it was put on to thick so they thinned it a little for me with Mineral Spirits. Which did help in applying the paint to the bed and head stock casting. Still the worst drying part is the pan with unthinned paint.
Thanks Chet

adh2000 · Aug 24, 2010

Enamels don't dry by solvent evaporation, they harden by reacting with oxygen in the air which causes the enamel to cross link into a hard polymer like coating. Your paint is not reacting and cross linking as it should. This could be because the paint sat on the shelf for so long before you bought it that the chemistry is no longer active. Usually in this case the paint is thick and goopy, thinning won't help, all that does is spread the goop out, it still won't cross link like its supposed to. Another reason could be exposure to UV (unlikely) but this could destroy the chemistry as well. Another possibility could be thinning with the wrong solvent. The wrong solvent could disperse the molecules so that they can't properly react. At this point you could try heat, every ten degrees doubles the reation rate, but most likely you are screwed. Remove the paint with solvent, throw the can away, buy a new can.

Alan

Rudd · Aug 24, 2010

Chet,
I recently painted my little horizontal mill, I used to work in an aircraft plant, we used epoxy primer on the planes. Really tough stuff. Called S-W, got quoted 220 for a 2 gallon kit... ouch.. I whined a little. The guy asked if I had an account.. No, should I? Well, it's 140 for the paint with an account. What do I need to open an account? A driver's license.

Stuff was really thick, looked like hell when I started brushing it, no leveling. They had told me to brush it straight. I had not bought the pricey thinner, but had some xylene on hand, which was to be used for cleanup. So I dumped a little xylene in, MUCH better.

I've had bad times with paint skinning "down heah" in the land of 150% humidity.
Again, the Japan drier is a good thing to know about if you need it.

OP says he is using Urethane Alkyd.. and manuf. says OK to thin, must not be enamel.

Interesting about the enamels, I don't use them much except for rattle cans. I know the stuff that comes out of a rattle can is a sight thinner than what comes out of a paint can. Wonder how they do that in light of your statement on cross polymerization being affected by thinner.

rbwillnj · Aug 25, 2010

Apologies, The paint I used was Sherwin Williams Industrial Enamel HS. I don't see any mention of urethane on the can. Penetrol is available in most paint stores, Home Depot etc. It works well in oil base and Alkyd paints. Don't know about Urethane.

What I do know about Urethane systems (I used to be a chemist) is that they need a catalyst to cure. In one part systems, the catalyst is generally moisture/humidity. If you applied your paint in very humid conditions, it may have been a factor in skinning the surface.

jimwallis · Aug 25, 2010

I have used a lot of different paints over the years but these threads lose me every time (probably because paint products are dummed down over here, they hardly ever really tell us what they are made of).

Is this a 2-pack paint system?
Anything I've used in the past with urethane in it's title I'm fairly sure was 2-pack, which leads to considerations of did you mix it right, or does one of the components have a short shelf life and had expired by the time you bought it (or was close enough to expire by the time you used it).
Should the paint be mixed by weight or by volume? Sometimes the different components have different density so it's important not to assume the ratio is the same for by weight or by volume.

Good luck working it out.

rbwillnj · Aug 25, 2010

Don't know about over there, but Urethane systems are available in both one and two part systems. Two part systems are generally sold for professional applications, but there are some exceptions. One part systems are quite common, Polyurethane varnish being a very common example.

Two part polyurethane varnishes are generally more durable and are often used in commercial applications, (like the bar at the pub, or the pub floor).

coyotechet · Aug 25, 2010

My out town friend who is now retried 30 plus year in the industrial paint busniess came over to help me with my paint problem. First thing he said is need to remove the paint from the pan an start over. He brought some paint remover with him and we had the pan clean and ready to prime within 90 minutes. We got it primed and will paint it tommrow. He said all the other parts that I painted where curing just fine. Said that the Urethane Alkyd Enamel was a very good choice of paint dries very hard. That I just picked a bad time to use it with the high humidity. The parts that I took to the basement shop are really getting hard and looking good. He said couple more day and they will be fully cured. with the temperature dropping this week he said that I should not have any more problems. He that Urethane paint is very fussy and some times darn hard to use but when cured is a very hard finnish and with a good gloss and color retention. Thanks to all

Chet

Jim Simmons · Aug 15, 2021

More success with Sherwin Williams Industrial Enamel HS and Penetrol.

I wanted to echo this previous post. I just shot my Bridgeport in my driveway on a still air day. Used 7 parts Sherw Williams Ind Enamel, 1 part Penetrol, 1 part xylene. I put one medium heavy coat on after three weeks of meticulous prep, and it came out like glass. I was shocked at the finish. It had a bit of orange peel as things settled, then all the peel just disappeared. Friggin amazing. Practically automotive. 70 dollar HPLV gun from Harbor Freight, with the reusable bucket kit (get the kit, it makes loading the paint so much easier). I got the paint code from H&W machine for the original Bridgeport color, and SW mixed it while I waited. I don't recommend their primer. Doesn't sand well. I just went straight over the Bondo. Glad someone on this list recommended the Penetrol. I even sanded a couple motors that I had painted with just paint so I could repaint them with this much smoother topcoat. The previous paint-only finishes definitely looked less than pro. It's funny what a difference that stuff makes. Gotta love the hive mind.

rbwillnj said:
Just for the record, I have used the Sherwin Wiliams Industrial Alkyd without any problems. It dried to the touch in a day, and hard in two to three days.

I did thin the as received paint with Xylene (the recommended solvent), and applied two thin coats with sanding in between. I also added a small amount of Penetrol to aid with leveling. I applied the paint with a very soft artist brush purchased at a local craft store.

Anatol · Aug 27, 2021

Chiming in late. Yeah, penetrol is good stuff

I've done a lot of painting with alkyd enamels, mostly on boats. Understanding viscosity is key. Applying paint too thick is a trap, it seems to be what happened for the OP. Too thick and you'll get the skin and it'll never dry underneath. Well, wait a year.
Multiple thin coats is always better, in my experience. Painting in hot weather I add mineral spirits, you can tell right viscosity by the way it rolls off the brush, too thick and the brush drags, you can feel it.

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