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Unread 05-13-2013, 02:36 PM   #1
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Epoxy primer giving a rough texture - DIY paint gun noob Q's

I bought a Harbor Freight spray gun set, have a 30 gallon compressor with water separator, and some epoxy primer. Using a 1.8 tip (can says 1.7 - 2.2)

I tried testing the pattern on a large piece of cardboard but after a while said "lets do this" and went for the hood (Jeep is apart). The finished texture looks like a bedliner, despite trying numerous adjustments. Is there a typical primary cause? Wrong pressure, too much paint, too close/too far, spray pattern too tight, bad mix ratio (4:1)?

I really don't know where to start. I was expecting to get runs and have a difficult time getting started, but not like this. I need to sand the entire thing and start over.

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Unread 05-14-2013, 07:55 PM   #2
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We'll it depends on the epoxy as to the eventual finish. Is it an automotive or industrial epoxy product?

An industrial product will have a rough texture if its designed to cover a media blast profile over the smooth surface it will be extremely rough. But if the product is an automotive grade (transtar, or the like) it will end up end relatively smooth but epoxy will always be a denser texture than your generic urethane primer and it won't sand worth a damn.

A good option would be reducing the product with a good urethane reducer, probably 10% to start. That would help and you could probably go a bit more, but I wouldn't go beyond whatever the Tds says. A lot of epoxies are actually 1:1 for use as a sealer.
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Unread 05-14-2013, 08:03 PM   #3
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I don't see anything about reducing on the product site: http://www.semproducts.com/product-c...ts/dtm-primer/

It is an automotive epoxy primer. I didn't purchase another primer and was planning to paint over this (after sanding with 600).
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Unread 05-14-2013, 08:23 PM   #4
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I am familiar with a lot of products but I have never dealt with that particular one. Though you could try to dial back your fluid delivery and bring your gun back about 8-10 inches from the surface.

What air pressure are you running?

If pulling the gun back and turning back the fluid delivery doesn't help further reduction may be helpful to get it to lay out better.

You may be alright going as much as 4:1:1 or possibly 4:1:2 with a good urethane reducer.

With out better knowledge of that SEM product there isn't much else I can say I'm afraid. But the tech line listed on the product sheet. Or where you bought the product.
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Unread 05-15-2013, 09:19 AM   #5
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Sounds like youre shooting too dry too much pressure and or too far from your panel. The material is drying in the air before it gets there and youre hitting it with a lot of overspray.

Looking at the site, its described as high build and easy to sand which i read as being primer filler. Filler usually lays on thicker and is designed to fill scratches etc as the basis for a smooth coat. Its designed to be sanded smooth.

And fwiw if youre looking for a smooth finish youre going to be sanding everything that you prime and wet sanding before the finish coat. And if your doing clear coat youll be wanting to wet sand and polish again. Its part of the process, lots of sanding. But done correctly you can end up with a finish soooooo much better than factory.
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Unread 05-15-2013, 09:43 AM   #6
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Quote:
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Sounds like youre shooting too dry too much pressure and or too far from your panel. The material is drying in the air before it gets there and youre hitting it with a lot of overspray.

Looking at the site, its described as high build and easy to sand which i read as being primer filler. Filler usually lays on thicker and is designed to fill scratches etc as the basis for a smooth coat. Its designed to be sanded smooth.

And fwiw if youre looking for a smooth finish youre going to be sanding everything that you prime and wet sanding before the finish coat. And if your doing clear coat youll be wanting to wet sand and polish again. Its part of the process, lots of sanding. But done correctly you can end up with a finish soooooo much better than factory.
Too much pressure and too little paint could be possible. I'm spraying in the 5-7" range that the can suggests. What causes it to dry in the air? Lack of paint or too much pressure?

I'll focus tonight on sanding the rest of my parts and prepping my other bay as another spray booth, and focus on getting everything primed this weekend with several coats. I'll put the time in sanding, and worry about final finish when I get to that paint and swap in the 1.4 tip.

Thanks for some feedback.
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Unread 05-15-2013, 05:19 PM   #7
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Do you have an air pressure guage on the the air inlet of the gun? Is it an HVLP gun? I've found a good rule of thumb is to make the "hang loose" sign with your hand putting the tip of your thumb on the end of the spray nozzle and the tip of you pinky finger on the substrate. Makes a pretty good guage of proper distance. I've never been a fan of dual purpose DTM primers. The aren't really true epoxy primers, but for budget and time purposes I guess they'll work ok. A true epoxy primer sands like trying to sand bubble gum, so a second primer surfacer step is usually needed if sanding is required.
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Unread 05-16-2013, 07:48 AM   #8
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Quote:
Originally Posted by bobthetj03 View Post
Do you have an air pressure guage on the the air inlet of the gun? Is it an HVLP gun? I've found a good rule of thumb is to make the "hang loose" sign with your hand putting the tip of your thumb on the end of the spray nozzle and the tip of you pinky finger on the substrate. Makes a pretty good guage of proper distance. I've never been a fan of dual purpose DTM primers. The aren't really true epoxy primers, but for budget and time purposes I guess they'll work ok. A true epoxy primer sands like trying to sand bubble gum, so a second primer surfacer step is usually needed if sanding is required.
Pressure gauge is at the tank, as is air/water separator. I should probably add another at the gun, but this is more or less a 1 time task. I'll try upping the PSI 5-10 and see what that does for me. If not, I'll just lay it on thick and plan some extra sanding. When it comes time to base coat, I'll do more practice before hitting the Jeep.
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Unread 05-16-2013, 07:54 AM   #9
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Quote:
Originally Posted by Jeeprage View Post
Too much pressure and too little paint could be possible. I'm spraying in the 5-7" range that the can suggests. What causes it to dry in the air? Lack of paint or too much pressure?

I'll focus tonight on sanding the rest of my parts and prepping my other bay as another spray booth, and focus on getting everything primed this weekend with several coats. I'll put the time in sanding, and worry about final finish when I get to that paint and swap in the 1.4 tip.

Thanks for some feedback.

Wow, 5" is way closer than ive ever shot paint unless i was trying for a run or sheeting. Usually going dry is too much pressure, too much distance. Are you getting an even pattern or kind of a straight line with a round spot on each end? It should be basically oval shaped on the test spray.
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Unread 05-16-2013, 08:04 AM   #10
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Quote:
Originally Posted by Indy View Post
Wow, 5" is way closer than ive ever shot paint unless i was trying for a run or sheeting. Usually going dry is too much pressure, too much distance. Are you getting an even pattern or kind of a straight line with a round spot on each end? It should be basically oval shaped on the test spray.
Paint says 5-7", I'm probably about 7 most of the time. I will try upping the flow and backing off air pressure. The pattern looks good, it is cigar shaped with no circles or uneven spray.
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Unread 05-16-2013, 08:30 AM   #11
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Bottom line is what Indy said about it being a high build primer..you won't get a smooth finish from it right out fo the gun,it's designed to sort of "fluff up" and thicken after sprayed so it will fill any pin holes and scratches,thats why the Tech Sheet data doesn't mention any reducer ratio,it's not designed as a final sealer primer.

You will have to to do a final sand before top coats no matter how good the gun sprays.

The general primers to have on a decent paint job is a High build for for the sanding and blocking..and a sealer primer for finish primer..a good Epoxy Primer will usualy reccomend a 20% reducer to make it a sealer and it will lay down about as smooth as a top coat if your gun is setup right.

I'll generaly strip or sand what i feel necesary,then spray an epoxy sealer primer and do all body work over that and when ready do a final epoxy sealer primer before the top coats,,this insures a good bond and even color coverage.

I feel you are going to have problems using that 30 gallon compressor once you start laying final coats..whats the CFM output on it?You may have to do a panel at a time and let the compressor catch up,but that also creates alot of moisture in the lines once the compressor kicks on...one or 2 water seperators won't work on a compressor like that, won't be good enough..you can make a makeshift remedy for the moisture in lines by using an old trash can or small barrel and wrap the hose around inside it,then fill the can with ice and put a good water seperator at the bottom side coming out of the can...this will efficeintly cool the air in the line and remove moisture that could ruin a could a good spray job.

Here's about the best write up i have ever seen on how to setup your gun for a spray..Barry is the owner of SPI and was and still is a well known high end painter before he started this company...
Adjusting Your Gun
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Unread 05-16-2013, 12:16 PM   #12
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The closest match I find to my compressor for sale online (it is an older Craftsman) is 33 gallon - with 6.3 SCFM at 40 PSI, 5.1 at 90. I'm pretty sure these are similar specs.

This is what I have to work with, and I'm not expecting show finish, just good. 1 panel at a time should be acceptable. The compressor builds pressure very quickly.
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Unread 05-16-2013, 05:55 PM   #13
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With a small compressor you'll want to go slow. It's hard to get an even coat when your pressure is constantly climbing and falling. As pressure changes so does the output from the gun. I've done rustoleum jobs with portables before, uneven finish doesn't matter cause you just throw a couple more on top of it. I likely wouldn't do a 'good' paint job using one since good paint costs more than $20/gallon But it's been so long since I've done a good paint job I'd probably prep and then hand it to the pro's anyway.

Actually I'm getting older and my bank account healthier, I'd probably just give them the keys and tell them to call when it's done.

But I'll rusto my offroad projects any day of the week

Back when I did my first car you ended up doing a ton of primer work, by the end of that you would have a pretty good hands on education as far as running the gun/pressures etc. And if you f'd it up, just sand it down and start over again. Primer was cheap.

And sanding OMG the sanding. I still wake up at nights haunted by the sound of a distant DA sander.


And then WET sanding, and then COLOR SANDING NOOOOOOOO! hehehehe. But I did have a purple mustang with a finish so fine you could read the smallest print in the reflection. Just a giant purple mirror after spending about 6 hours per panel color sanding and buffing when it was done. It was a long project., 3 hours a day, 5 days a week minimum for a year on just the body.

Then a few years later I traded the mustang in, 2 months later the nimrod that bought it wrapped it around a tree.
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Unread 05-18-2013, 03:23 PM   #14
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Originally Posted by Jeeprage View Post
The closest match I find to my compressor for sale online (it is an older Craftsman) is 33 gallon - with 6.3 SCFM at 40 PSI, 5.1 at 90. I'm pretty sure these are similar specs.

This is what I have to work with, and I'm not expecting show finish, just good. 1 panel at a time should be acceptable. The compressor builds pressure very quickly.
8.6 at 40..., 6.4 at 90. I just double checked.

Things are going better now, getting the hang of things.
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