E-Bodies.org Cuda Challenger Forum

Technical Shop => Body Shop => Topic started by: fireguyfire on May 05, 2020, 11:08:41 PM

Title: Primer blocking question
Post by: fireguyfire on May 05, 2020, 11:08:41 PM
Just about ready to shoot the colour on my 73 challenger.
So far I gave the bare metal 1 coat of epoxy, then did my body work,then another coat of epoxy followed by a good coat of high build.
I blocked the high build with 180 and the body work is real good.
I then shot another coat of high build (hoping my last) and just blocked it with 400.

The result is 99% excellent, but there are 5 or 6 small spots, mostly on door or trunk lid edges where I went through to the metal; again you have to really look close to notice.
My question is, how should I deal with these few spots? The car certainly doesn't need another full coat of high build; that would be a huge waste.
Can I just spot prime these spots with a detail gun?
I also saw on YouTube a guy who just hit his similar spots with small amounts of epoxy to seal them up, then sprayed the colour on the entire car once the epoxy on those few spots had flashed.
What would you experienced paint guys and gals suggest I do?
Title: Re: Primer blocking question
Post by: fireguyfire on May 05, 2020, 11:31:26 PM
I also saw in a auto painting book that the author suggests after all the priming and blocking, and when you are ready to shoot the colour to hit the car with a coat of epoxy to seal it and then once that flashes, to paint the colour.
This method would solve my small burn through issues.
Title: Re: Primer blocking question
Post by: Marty on May 06, 2020, 04:32:02 AM
Quote from: fireguyfire on May 05, 2020, 11:31:26 PM
I also saw in a auto painting book that the author suggests after all the priming and blocking, and when you are ready to shoot the colour to hit the car with a coat of epoxy to seal it and then once that flashes, to paint the colour.
This method would solve my small burn through issues.

That's the ticket.  :bigthumb:
Title: Re: Primer blocking question
Post by: JS29 on May 06, 2020, 06:43:47 AM
Primer sealer is always a good idea. the epoxy primer can be reduced to be used as a sealer. read the instructions and procedures and you will be fine. :alan2cents: The system i use is made by Exalta Formerly Du-Pont. It is caller value shade. You find the # on the can of base, Mix that color and spray. You have uniform color and you use less base coat. Same go's for single stage, you can get the job done with less paint product.  :alan2cents:   
Title: Re: Primer blocking question
Post by: Rich G. on May 06, 2020, 07:00:02 AM
I agree, one coat of primer sealer and then color. Make everything uniform and the best part is you don't have to sand it!
Title: Re: Primer blocking question
Post by: fireguyfire on May 06, 2020, 07:52:39 AM
Thanks for the advice gents.
I looked at the technical data sheets that cane with my epoxy primer, and it mentions nothing about thinking for use as a primer/sealer; just regular use ratio of 4:1:1.

Anyone got a suggestion how to thin for sealer use?
Title: Re: Primer blocking question
Post by: JS29 on May 06, 2020, 08:38:45 AM
What brand of epoxy have you got?  :notsure:
Title: Re: Primer blocking question
Post by: 1 Wild R/T on May 06, 2020, 09:22:16 AM
I'm surprised no one else has mentioned it but the jump from 180 to 400 is a pretty big step & I'd be surprised if there isn't some 180 scratches hiding waiting for color to be laid down before they become visible....

Typically from 180 you step to 240 then 320, 400 & possibly 500....
Title: Re: Primer blocking question
Post by: fireguyfire on May 06, 2020, 09:27:24 AM
I blocked the 1st coat with 180; then sprayed another coat of high build over that, then blocked the second coat of high build with 400; was slow but it is very slick.
I'm debating on taking it to 600 before the sealer coat
Title: Re: Primer blocking question
Post by: 7E-Bodies on May 06, 2020, 09:32:20 AM
Good stuff here. I'm about to enter this stage as well. Hoping @Cuda Cody (https://forum.e-bodies.org/mlist/cuda-cody_1) chimes in as well since I'm following his written protocol through the whole project. I guess my concern about adding a final coat of epoxy before color is covering a nicely sanded surface with a slightly rougher surface of epoxy.

Kevin
Title: Re: Primer blocking question
Post by: Cuda Cody on May 06, 2020, 09:45:22 AM
PPG DP makes a great sealer and will solve your bare metal issue.  400 dry or 600 wet is good.

https://www.e-bodies.org/how-to-paint-a-show-car-step-by-step-guide/

Just mix it slightly different when using it as a sealer.   Mix at the 2 to 1 to .5 blend ratio will result in a 5.0 VOC sealer.

https://www.e-bodies.org/Resources/Mopar_How_To/p196_DP_epoxy_primer_ppg_dplf_product_sheet_196_dp40_dp48_dp50_dp74_dp90.pdf



Title: Re: Primer blocking question
Post by: Rich G. on May 06, 2020, 10:35:20 AM
If you used a guide coat when you did your final sanding you would know if you left any sanding scratches. The primer sealer is very thin that's why you can get away from sanding. I'm just finishing up a cuda using Cody's painting tips.
Title: Re: Primer blocking question
Post by: fireguyfire on May 06, 2020, 10:36:02 AM
Yup; used a guidecoat
Title: Re: Primer blocking question
Post by: tparker on May 06, 2020, 10:40:08 AM
Just a side question. What exactly is a sealer, or why is it called that? When I think of a sealer, I think of it being sealed off. If I remember correctly my primer said just reduce more and it is now a sealer. To me it is just "watered" down primer. How is it sealing where the primer wouldn't?  Just curious on the details.
Title: Re: Primer blocking question
Post by: fireguyfire on May 06, 2020, 10:49:45 AM
I'm using BASF Limco LR20 epoxy primer; it's a 4:1:1 mix ratio so I'm not sure how I would thin it out to use as a seal coat
Title: Re: Primer blocking question
Post by: JS29 on May 06, 2020, 12:07:36 PM
Go to there web sight. But off the top of my head you reduce it more, It sprays out finer and smother.  :alan2cents:
Title: Re: Primer blocking question
Post by: Cuda Cody on May 06, 2020, 12:37:46 PM
 :iagree:  Sealer lays down smoother for the final paint.
Title: Re: Primer blocking question
Post by: fireguyfire on May 06, 2020, 01:04:36 PM
Ok; I'll go to their site; I'm guessing 4:1(activator):2(reducer) might be about right
Title: Re: Primer blocking question
Post by: JS29 on May 06, 2020, 02:57:19 PM
Quote from: fireguyfire on May 06, 2020, 01:04:36 PM
Ok; I'll go to their site; I'm guessing 4:1(activator):2(reducer) might be about right
That would be a good guess!  :yes:
Title: Re: Primer blocking question
Post by: fireguyfire on May 06, 2020, 03:02:44 PM
I see in my mixing cups there is a 4:1:1.5 column, so that might be it.
Title: Re: Primer blocking question
Post by: JS29 on May 06, 2020, 03:15:13 PM
That sounds about right. Still check with the manufacture first.  :yes:
Title: Re: Primer blocking question
Post by: fireguyfire on May 06, 2020, 03:56:15 PM
Found the mixing ratio on the BASF site for use as a sealer; instead of 4:1:1 it needs to be mixed 3:1:1
Title: Re: Primer blocking question
Post by: JS29 on May 07, 2020, 06:30:40 AM
 :cool:  PPG is more reducer from what i remember.  :ohyeah:
Title: Re: Primer blocking question
Post by: torredcuda on May 09, 2020, 05:47:10 AM
Quote from: tparker on May 06, 2020, 10:40:08 AM
Just a side question. What exactly is a sealer, or why is it called that? When I think of a sealer, I think of it being sealed off. If I remember correctly my primer said just reduce more and it is now a sealer. To me it is just "watered" down primer. How is it sealing where the primer wouldn't?  Just curious on the details.

Different types of primer or primer/sealer - laquer, polyester, epoxy etc., sealer or primer sealer does what it says - seals off underneath layers. Some decent info here - https://www.rodauthority.com/tech-stories/paint-body/primer-sealer-choices/
Title: Re: Primer blocking question
Post by: Rich G. on May 09, 2020, 06:13:44 AM
Very good article. That pretty much sums it all up. I think Earl Schibe might have skipped a few if these steps. Parts and labor $19.95 ahh the good old days!
Title: Re: Primer blocking question
Post by: JS29 on May 09, 2020, 07:24:45 AM
Earl Shibe!  :haha: :rofl:  :rofl:
Title: Re: Primer blocking question
Post by: jimynick on May 10, 2020, 07:52:12 PM
Quote from: Rich G. on May 09, 2020, 06:13:44 AM
Very good article. That pretty much sums it all up. I think Earl Schibe might have skipped a few if these steps. Parts and labor $19.95 ahh the good old days!
Man, I remember those commercials! "Hi, I'm Earl Schibe and I'll paint your car for $29.99", but then I can remember my old man painting used cars for $65 back in 1971, at a Chevy dealership!  :looney:
Title: Re: Primer blocking question
Post by: JS29 on May 11, 2020, 05:37:53 AM
@jimynick (https://forum.e-bodies.org/mlist/jimynick_55)  You remember what a gallon of paint cost in them Thar days? Straight enamel no dough.  :cheers:
Title: Re: Primer blocking question
Post by: jimynick on May 11, 2020, 11:23:42 AM
Not off-hand regarding the paint prices, but I know I was working for $2.00/hr if that helps. Our enamel line was RM and our lacquer line was DuPont. There was no dismantling and it was a tape 'er up and scuff 'er off and shoot it. Dad said he made a little money on the deal, too. In '78 I was working in a Maaco and the top of the line paint job was $169.00  There was no such thing as clear coat in the sense we have it now and you only saw it on custom cars and it was all lacquer based, so you could count on it cracking in a few years. I remember the old guys used to put the pot of paint on a hotplate and heat it up! They swore, and to be fair to them it did, make the paint go on smoother and shinier, but it'd run in the blink of an eye and only the real old fashioned painters could get away with it. Tempus fugit!  :cheers:
Title: Re: Primer blocking question
Post by: JS29 on May 11, 2020, 11:31:56 AM
Ya clear coat in any thing but lacquer Did not exist until the mid later 80's.  :alan2cents: