I originally sent a pm to Lloyd about this and got a couple of ideas but still not sure of the reason why. I'm in a death match with the engine bay painting of an OT but the issue is about paint. It has the typical rounded wheel houses, horizontal, and vertical areas all in a rather tight area. Using PPG Shopline acrylylic urethane single stage with hardener (sprays like KoolAid). First time I buggered it a bit because my Finishline gravity fed HLVP gun was too big to reach the nooks and crannies and got about six runs and not complete coverage. Sanded with 320 and 400 grit paper and then reshot. I used a siphon feed touch up gun and it was great to get into all the areas but because I had to shoot at bad angles I got a couple of drips and then the vent hole must of clogged up and I got spurts rather than a nice spray. Trying to save the situation I must have got too much paint on during the second coat. Left it from Saturday until today and went at the runs. I noticed the paint was gummy when sanding and in some places it seemed a little bit sticky. I'm thinking I have to sand the whole area to break the very top film so the layer beneath it can cure. I used temp appropriate reducer and hardener but the then the temp climbed about five degrees above the recommended range. So a couple of questions.... how do I get the paint to cure and not be gummy and should I continue with 320 and 400 grit paper? Lloyd recommended taking a rag and washing the paint with lacquer thinner and let it dry overnight and to only use a red scotchbrite, though I've tried a grey one. Any ideas guys for what to do and what's caused this buggery? I'm doing a body off and this has been the very worse part of it! All in preparation to begin working on my '32 (HAMB friendly content! LOL).
I would stick it out in the hot sun for a couple of days,then wet sand it and reshoot it.You can buy a small detail gun that works good for these funny areas to paint.If your gun is spitting,the packing nut is loose on your needle. good luck harvey
Show us your spray pattern, Put thinner in your gun, shoot onto cardboard, post the pic. Are you shooting tack and flow coats? In an uneven area like an engine compartment, I just shoot multiple tack coats with a shorter recoat time, it covers and lays down after 2-4 passes
To keep the vent hole from dripping on your work when you have to tip the gun too much, I wrap a rag around the gun to catch the drips. Let it cure, sand it with 500 and reshoot it with slightly over thinned material, light coats.
I got the spurting issue retrified, I know about the rag wrap but unfortunately I had to hold the gun almost upside down to hit the area I wanted to, and my spray pattern is fine. I'm going to shoot a couple of more coats to tidy everything up. My biggest concern is the stickiness when sanding and why the paint hasn't turned rock hard. Last time I shot this material it was rock hard after about 18 hours when I checked it. I'm worried that it won't harden up enough to re-shoot. Anybody else have any ideas/solutions?
Is this the paint you added way too much hardener too? As much as it seems counter intuitive excess hardener can actual cause paint to not fully cure. If it is it may never fully cure as there was not enough active ingredient in the paint to activate all of the hardener. Time to strip it off.
My sins are being revealed! No, that issue apparently wasn't an issue at all. Paint hardened up very well as attested to by taking out some runs. But I decided to do a couple of coats to make things tidy. I had a disasterous session and I'm getting a wee bit pissed off so time to regroup. I went back at it this afternoon and most of the paint has hardened up but there are a couple of areas that still seem to be sticky if I try to sand on them. I'm thinking that they will be okay by morning and hard enough to paint over. However, what do you think would happen if I spray over the sticky areas? Maybe I'll leave it a couple of more days to make sure it hardens up. The big question to me is why it became sticky. Mixed correctly and used the temp appropriate hardener and reducer but as I said the temp spiked a couple of hours later. So I'm thinking it was that or perhaps I put on too thick a layer of paint and it skimmed over not allowing proper curing. What do you think as I value your opinion.
We struggled with paint on an OT vehicle. The headaches ended when we used a kitchen scale to measure the components. The paint was waterborne and so had to start with a clean sheet as it did not spray like conventional paint. Weighing the components gave us a more consistent result with a finish to be proud of. Place the container on the scale, zero the scale and then pour in the weight for the batch. Best suggestion may be to give the paint about 5 days and then try to sand it with water mixed with some drops of Dawn dish soap added to the water for some lubricity and may less stickiness. The Norton clog resistant sandpaper seemed to work the best and last longer. Feel your pain and hope it gets better.
Check the age of the hardener. Just because it may be new from the store doesn’t mean it’s still good. Could be too thick possibly. Or not enough flash time. Sometimes we get in a hurry and do not properly stir the components. This usually leads to the issue you described. The temp range really only affects how it flows. Meaning, a fast hardener when its 90 degrees will tend to have a lot of orange peal. A slow hardener when it’s cold will tend to run or sag if you try to spray it slick. I’ve shot a good bit of shop line. For single stage, the regular PPG reducer helps it a lot. Lays down much better. Costs more but looks better, less peel. I prefer a BC/CC for areas like that. With single stage your trying to achieve coverage and gloss at the same time. This leads to more runs and sags. Or, and this will sound counter productive, over reduce the single stage and spray the first couple coats like a base coat to achieve coverage. Give extra flash time. Then spray a couple slicker coats. Now your just working out the gloss. Sounds like you may need a gravity feed touch up gun. I have a cheap HF one that sprays really good. But for paint, especially single stage, it will need over reduced to spray out of the 1.0 tip that most touch up guns have.
Aged hardner/activators opened or not can cause issues. Wish I had some spare time to figure out a pressure pot for small sprays like engine compartment. Love my pressure pot for those jobs, but it needs extra paint to load, spray and then cleaning it. But I guess in your situation throwing some paint away would be better
Hardener is usually the culprit if there is an issue. Did you purchase it recently? If so did you buy from Lordco? They are terrible at having old stock on their shelves. I get warranty claims every quarter from them and half the stuff is stock that has been sitting on their shelves for years. Other than that did you wipe the surface down with anything before spraying the new coats? I see it often where guys wipe with a slower evaporating solvent and then spray almost immediately after wiping the surface not giving the solvent enough time to evaporate off the surface.
Yes I think I'll get a gravity feed touchup gun. My current one has a 1.4 or 1.5 cap which is nice. I did buy the materials from Lordco so maybe that's an issue. I cleaned the area well (OCD) and for the final wipe I used rubbing achohol and I tacked the following day before painting. Going to pick up a pint of paint now and I'll ask about the regular reducer, thanks for the tip! I'm going to leave it until the weekend before final , hopefully, sanding and re-prep for paint.
If the paint thickness is more than you would have on a flat surface without running, you could have an issue with that. I have had mistakes that took more than 24 hours to dry enough to sand even with water.
I hope you learned your lesson.... Don't work on off topic cars.... Stick to hot rods....lol.. good luck
Personally I wouldn't spray a new coat over the sticky stuff because if it's still releasing solvents it might blister up through your fresh coats. Thirty years ago whilst working in my Dad's panel shop I did a full respray on a Holden Panelvan using metallic acrylic lacquer. Several coats with a sand between followed by a couple of coats of clear. Left for a week and colour sand with soapy water and fine grit and buff. Looked sensational. Two weeks after the customer picked it up it was back with little blisters in the paint especially the areas subject to direct sun. Stripped it back to the primer and redid it. Came back a month later with same thing and with pissed off customer. We got the PPG rep to have a look at it and he took a sample panel for analysis. Turned out the customer had been taking it home and wax polishing it,driving it to the RAAF base he worked at and parking it in the blazing sun. The solvent had not been able to fully dissipate because he was locking it in with wax coats. We redid it again to pacify the customer but told him no more comebacks.
Update: Well I sanded down the sticky stuff after I gave it four days to "cure" and it was a bit of a bugger. Re-shot and all is good except for the inevitable dust specks which will disappear when I cut and buff. I think the problem with the paint was instigated by me not having enough circulating air in my shop and also not leaving the fans on long enough. Lesson learned. I ran my fans for 12 hours and the paint cured hard as rock. I just wanted to give a shoutout to Lloyd and Anthony. They gave some good advice and Anthony especially restored my confidence. So thanks guys!
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