Newb question about primers

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inspectorbob

Can someone explain to me what determines when you need to use a 2k primer over epoxy vs. just using base directly over the epoxy? I've seen reference to doing both ways, but I don't understand when to use the 2k.

Thanks!
 
2k urethane is used when you need more build to block out.
 
exactly, 2K urethane is designed for build, a primer/surfacer for filling imperfections.
 
You will find a lot of reference to "all epoxy" jobs on this site. This technique uses epoxy as a blocking primer for increased chip resistance and durability. This method is only recommended for experienced and very patient individuals, however.

Unless your car is nice and straight and you are doing a "skuff and shoot" you should most likley use 2k. It sands easier and cures faster than epoxy.
 
If experience is limited, and patients and time aren't a problem.. does blocking the "epoxy only" job take more talent or just slower? The "added durability" benefit of epoxy only sure is a big upside.
 
Thanks for the responses! So, even the regular 2k is used for build, or is it just the high-build?
 
Mule;17738 said:
If experience is limited, and patients and time aren't a problem.. does blocking the "epoxy only" job take more talent or just slower? The "added durability" benefit of epoxy only sure is a big upside.
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I have limited experience as well. I havent had any problem using SPI epoxy this way. Aside from experience and time, you will also need heat. Trying to use epoxy in cool weather is a up hill battle for me.

Here are some dos and donts from what I remember shine telling me.

Spray one wet coat at a time and block it.

Use coarse paper like 100 until everything blocks evenly

Dont spray medium coats, or the epoxy could bridge the sanding scratches rather than filling them.

Im sure there is more, I am hardly an expert on this.
 
inspectorbob;17742 said:
Thanks for the responses! So, even the regular 2k is used for build, or is it just the high-build?
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You can use either one, depending ho much build you need. Barrys regular 2k probably builds about the same mils as some of the majors high build primers.
 
Finishing off in just epoxy does require patience like stated above. I have been doing it this way ever since using SPI and one thing I believe it does is it teaches the tech to not rely so much on primer filling things it should be filling. I know it really helped me fine tune my metal working skills along with my blocking skills. For someone with less experience a qualitly 2K primer will work just fine, nothing wrong with doing it this way.
 
if you mix epoxy the day before, shoot it with a 2.0 -2.3 gun , double coat it , you can get plenty of build. i'm weird. i do not stack anything but color and clear. i block each coat of epoxy . start at 100 and move up each coat . your building the low's . leave no epoxy on ridges or edges until your last two coats. leave it for a week then seal and paint. seems to work really well. i'm old so i limit the number of products in a job...... less chance i will screw it up.
 
I did the Ranger with spi epoxy, shot double wet coats w/ 1.8 tip in lph400, worked awesome.
It was my first time using the SPI epoxy and the results were awesome.
I think the guys advice about blocking and shooting wet are true for any priming.
Primer is easy to spray dry and bridge sanding scratches, and I think for me it is easier to do that with the 2K product than when using the epoxy.
Another thing I like is being able to use the left over epoxy the next day or two, adding to it and using it instead of throwing it away.
 
Senile Old Fart;17770 said:
I did the Ranger with spi epoxy, shot double wet coats w/ 1.8 tip in lph400, worked awesome.
It was my first time using the SPI epoxy and the results were awesome.
I think the guys advice about blocking and shooting wet are true for any priming.
Primer is easy to spray dry and bridge sanding scratches, and I think for me it is easier to do that with the 2K product than when using the epoxy.
Another thing I like is being able to use the left over epoxy the next day or two, adding to it and using it instead of throwing it away.
Click to expand...

Good point. I love not having to waste unused primer because I mixed too much or running out because I mixed too little. When I am working steady on a project, I always have epoxy mixed in a sealed container waiting to be sprayed.
 
i have no problem blocking cured epoxy with 220 then 320 dry. i keep a shop vac nearby and vacuum up powdered epoxy and unclog sandpaper...
 
The 65 Vette I just finished up was put into the last coat of epoxy around the first of jan. 2 coats with 20% reduction. We wetsanded it with 500 before paint and shot another coat of epoxy reduced 50% as a sealer.

the 1.5 month old epoxy sanded just fine. Exceptionally well, as I was thinking it would be a little tougher than 2k primer. Was about the same when doing it wet with 500. I tried this once with sikkens epoxy back when I was using it, and cursed every minute of sanding it. The sikkens epoxy was only a few days after spraying.
 
just 1:1 . by letting it set it gets some body. the 2.2 will put on a good coat. i do a double coat instead of hosing it. seems to build just as good and less chance of some hangers . i'll do 3 coats or 6 coats or 10 coats . whatever it takes. i dont keep track of it so i dont know how much longer it takes.
 
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