Paint/Body Corvette Materials, Techniques, and How To

thinning epoxy primer for sealing

Old 04-26-2019, 08:49 PM
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Default thinning epoxy primer for sealing

Question for the group or DUB. after doing some fiberglass repair in all different spots of my car I sprayed PPG shopline brand epoxy primer over the area's that were stripped/sanded beyond the old paint layer ( exposed fiberglass) maybe 1/3 of the car to seal it up. I'm going to lay on some 2K primer to do more boarding & sanding then re-seal before paint. The paint tech at the local paint store said to just reshoot the car with the same epoxy but to thin it out with acetone if its the last sealer coat, he didn't specify why, do I want the sealer coat to be real thin?
Also I have 72 hour window to lay my base coat on, i plan on shooting my last sealer coat then spraying my base the next morning 12 hrs later. If I cannot then I have to scuff the epoxy with a red scotchbrite pad, is that sufficient before I shoot the base?

Last edited by Lyndwood; 04-26-2019 at 08:49 PM.
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Old 04-28-2019, 09:50 AM
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I would CALL and verify that using acetone to thin this epoxy IS the recommended solvent to thin it down and HOW MUCH you can put in it to do so.

Thinning an epoxy down for a sealer; coat is a common practice sop the film thickness is not to thick and it seems to lay flatter and not want to create any 'orange peel' effect....which in turn...causes problems when you apply some colors due to it can telegraph this orange peel effect in the actual when clear is applied on it you can see the texture in a metallic color.

I know that the 'window' of the epoxy allowing paint to still chemically bond to it is 72 hours as you stated....BUT.....the longer you allow the epoxy sealer to dry...the moisture and other contaminates can get on it and also cause for POTENTIAL issues in the future. So....when I seal a car...I wait the required amount of time to let it flash off adn then may give it a bit longer due to current air temps and then apply the paint as soon as possible.

YES...In some cases scuffing the sealer coat is needed due to an issue that occurred during its application and applying the base was not a wise thing to do. I ONLY do this when I have to and d DO NOT make scuffing a sealer a common is just more work....and in doing is more crap that is now in the booth that I have to contend with POSSIBLY getting in my paint job when painting it..

KEEP IN MIND...that IF you allow the sealer to go past the 'window'...then ALL of the surface needs to be scuffed WELL due to where ever you do not scuff it....the paint may not be able to link to it and POSSIBLE delaminate in the future. Which is another reason WHY you really do not want to loose your window and loose the compliance of the products linking up.

For what this is worth.....I would advise you starting your paint job in the morning and shooting it until it is completed. On some jobs I can start at 8am and finish at 5pm. Giving each coat sufficient time to flash off due to current air temps....if they are colder than normal.


Last edited by DUB; 04-28-2019 at 09:51 AM.
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Old 05-02-2019, 07:53 AM
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You don't mention exactly what PPG sealer you are using. I have used PPG DP90 and DP90LF for years. The spec sheet has an option to reduce or thin down the sealer with DT reducer or acetone. The key is in the ** footnotes on the spec sheets. See attached link. The reason your paint rep stated to use acetone is that it is an automotive application with more strict VOC requirements. My personal preference is to use the DT reducer (use whatever temp reducer you will be spraying in i.e. DT 860 for example,) One reason is that you aren't sure on the quality of the acetone whereas if using a PPG DT reducer the product quality is per the PPG specs. I don't like cross breading products but that is just me. The sealer lays down a bit better with less build up but not much less. Refer to the mixing ratios and you will see what I am talking about. To note I use a crappy 25 dollar primer / sealer gun to lay the sealer and primer down. When adjusted and used correctly the gun doesn't make a huge difference with sealer and primer provided you are using the correct fluid tip size, my top coat gun is a expensive Sata gun but top coating is a totally different topic. On DP sealer you have a 1 week window. You might have a different window if using a different PPG sealer. Again check the spec sheet for the sealer you are using. See page 2 of the spec sheet for DP90LF. Don't go by what the counter guy says as gospel get the spec sheets and read and understand them fully. The PPG sheets are quite easy to read and understand. I am repainting my Nova now and just laid down the sealer and K36 primer last week and reduced the sealer. When I painted my 66 Vette 3 years ago I also reduced the sealer. If you want extra film thickness just do another coat. Also one thing to note is that DP sealers sand like complete crap. They gum up sand paper quite badly it is not a sanding friendly sealer. So at all costs avoid runs. Do more lighter coats than less heavy coats.
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Old 05-03-2019, 08:53 AM
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As mentioned above it DOES make a difference on which epoxy you are using due to the commercial grade I use....required acetone to thin it by 5%....if needed.

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