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  #91 (permalink)  
Old 07-20-2013, 09:28 AM
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Maybe I'm wrong but a polyester primer like slick sand is catalyzed with the same catalyst as fiberglass resin and should have water resistant qualities. As long as it is a liquid hardner (not a creme hardner), I don't see an issue...correct?

Just did a quick search.

Slick Sand Gallon



Ray

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  #92 (permalink)  
Old 07-20-2013, 09:36 AM
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Quote:
Originally Posted by 69 widetrack View Post
I don't see an issue...correct?
Ray, you probably are right (and lord knows you're the pro here and I'm certainly not)....but you're the FIRST person I've ever seen say this. The only thing I've ever heard, ever learned, ever known, is to never wet sand a sprayable body filler/poly primer. Now on their low VOC Slick Sand Evercoat said it was wet-sandable.

Barry says he wouldn't wet sand polyprimer in a million years.

Now my car has a lot of Slick Sand on it, there are spots where it did get wet when I was wet sanding (I sprayed 2k over it to wet sand), or where the 2k sanded off and then I was sanding slick sand. When I did it I immediately hit it with the blow gun, and when I was all done I pushed the car outside and let the sun beat down on it and get it hot.

I haven't had any problems, and I know other people have gotten away with it. Just passing along what I've heard, from reliable sources.

Last edited by Lizer; 07-20-2013 at 09:43 AM.
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  #93 (permalink)  
Old 07-20-2013, 10:28 AM
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I'm not saying your wrong, I personally have used slick sand when a customer has provided it and have been told that if a product has a liquid hardner it is okay to wet sand....for me, I would prefer not to use it...I prefer an Epoxy primer with a 2K primer over top and now that I'm using SPI Epoxy with it's sanding qualities, I hope to minimize the use of 2K primer all together. In the case of the OP, he did Epoxy prime the entire car, I can't recall if he used a 2K primer (I believe he did) or a polyester primer but, he used an Epoxy to start with so he would have a product that would resist water getting to the metal or filler even if he did wet sand a polyester primer. This is all good information Lizer and things that people should be aware of...if Barry suggests not wet sanding polyester primer, I would then not wet sand polyester primer...again for me, I would prefer not to even use polyester primers like slick sand...but...that's for me and to each their own.

Ray
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  #94 (permalink)  
Old 07-20-2013, 10:47 AM
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I think the fear isn't so much of the metal rusting beneath or underlying filler getting wet, but the Slick Sand itself coming up if wet sanded.

What's the benefit to a liquid hardener over the creme hardeners that they can get wet?
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Old 07-20-2013, 11:34 AM
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You could very well be right about the slick sand lifting and the way I see it is that for one gallon of slick sand you get 4 small tubes of liquid hardner...making the amount hardner you add to a certain amount of primer somewhat less than an accurate measurement. If you don't add enough hardner it may not catalyze the resins in the primer thoroughly and would make it uncured and porous,,,it would still dry eventually but not cured as opposed to a 2K primer where the mix ratio is 4 to 1 ... if your off a little, it may not make as big a difference when compared to being off a little with liquid hardner in slick sand.

The resins in slick sand would be comparable to the resin used in fiberglass work as they use the same liquid hardner and the fiberglass resin is water proof...creme hardners used in plastic fillers and plastic fillers being porous to begin with (by design) use different resins than the ones found in fiberglass.

I am by no means a chemist, nor do I profess to be. When I have asked questions about wet sanding slick sand, the answer has always been yes for the reasons I've described however, I can see a problem, as you described, arising if someone was to not add enough hardner to the product.

Ray
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Old 07-20-2013, 05:54 PM
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I will add an experience I have had with poly primer as that is what I use quite often for my rough blocking. I have never wet sanded poly primer for the main reason that it is very porious and will act as a sponge, have used quite a bit of slick sand in the past but have found a poly made by dura tec that sands unbeleiveable easy. Well any way this poly primer is labeled as a BASE primer and must be topcoated with a 2K or epoxy because it is so absorbant. I had a problem with part of this sanded and uncoated poly primer getting wet by accident and very shortly after that I had noticed huge blistered bubbles taking shape exactly where it had been wet. Now this car was epoxied using SPI then skimmed then poly primed, don't you know that blister went right down to bare metal and leaving rust on the metal under the epoxy. In other words it came right off in sheets taking the filler work and the epoxy with it. I was pretty surprised this stuff bonded itself in a way that it became one layer right down to the epoxy. Bottom line is I am now convinsed that any water added to a porous poly primer is just asking for a failure.
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Old 07-20-2013, 06:17 PM
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That's good information Dennis and i appreciate you sharing your experience. The last time I used slick sand would have been about 3 or 4 years ago as the customer insisted and I guess I must have been lucky, the car still looks good today. The car did have 2 coats of PPG's DP Epoxy underneath it and the manufacturer (Evercoat) suggests wet or dry sanding. In the future I will avoid using the product as I like wet sanding my primers.

Ray
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  #98 (permalink)  
Old 07-20-2013, 06:30 PM
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Ok here is a curiosity question. I have no experience with waterborne paints, but I know some of you do. On evercoat's page, most of their poly primers say they don't require a sealer and are waterborne compatible. If wet sanding is a problem due to the porous primer, why wouldn't the waterborne paints not cause problems? Again this is probably a dumb sounding question, due to my lack of knowledge about the water borne products. Thanks in advance for the education.

Kelly
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  #99 (permalink)  
Old 07-20-2013, 06:57 PM
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I think it's a great question Kelly and you are correct Evercoat not only recommends wet sanding, they also do state that the product is water born base compatible. This is the same information I used several years ago and I still do believe that if the polyester primer if catalyzed properly it is water resistant for the reasons I explained in a previous post.

Now to try and explain why water born base coat could in fact be compatible with Evercoats Slick Sand. If we take PPG's water born base coats the reduction is as follows 10% "water/reducer" for solid color, 20% for metallic's and pearls and 30% for the mid coat in a tri coat...the reduction is minimal in comparison to solvent base coats at 1 to 1. The other factor is that even though it is a water born base coat, it does have approximately 15% solvents in the "water/reducer", so with minimal "water/reducer" reduction and a solvent content in the "water/reducer", any product with a catalyst should be able to withstand a mist of water born base coat, I would hope, if it didn't, why would anyone even consider using it. It would be similar to wiping it off with a damp cloth.

Still, my opinion remains that it should be safe for wet sanding if catalyzed properly and as I said, I'm not a chemist, I prefer products that aren't considered a "body man in a can" and I like to measure the amount of hardner I put in my primer with a measuring stick.

Ray
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  #100 (permalink)  
Old 07-20-2013, 07:15 PM
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Oh, and Dennis, please understand, I'm talking about "Slick Sand", I haven't had any other experience with any other polyester primers and I in no way was commenting about any other product.

Hope there isn't any misunderstanding.

Ray
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Old 07-20-2013, 09:17 PM
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The tech sheet for my gallon of Slick Sand makes no mention of wet sanding whatsoever.
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Old 07-21-2013, 06:23 AM
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Thanks Again!,
After I am done with the filler(s) Can I spot prime using epoxy primer over the top? Will that work ok with the poly primer surfacer underneath?
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Old 07-21-2013, 07:38 AM
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Quote:
Originally Posted by 69 widetrack View Post
Oh, and Dennis, please understand, I'm talking about "Slick Sand", I haven't had any other experience with any other polyester primers and I in no way was commenting about any other product.

Hope there isn't any misunderstanding.

Ray

No Ray, there is no misunderstanding here. I was reffered to this Dura Tec poly through a good friend of mine that has been using it for a while now. The sanding qualities of this product is hands down the best of any poly I have ever used, and I have used a lot of them. This one does require mixing with a scale, most polys do not. That is a critical part of using this as to how it will harden. Then it can be reduced 10-15% with lacquer thinner to spray it out easier. I mainly use as a final skim coat instead of the filler, because of the sanding features, as most polys sand like cement. But the downside is it absolutely can not get wet at all until you topcoat with a urethane or epoxy primer. I have as I mentioned earlier never wet sanded any poly previously, but this dura tec poly is not your typical poly as a slicksand or feather fill. Still don't feel comfortable wet sanding any thing other than epoxy as even 2K urethane primers will absorb any water, the epoxy will always bead the water off.
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  #104 (permalink)  
Old 07-21-2013, 08:19 AM
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Thanks Again!,
After I am done with the filler(s) Can I spot prime using epoxy primer over the top? Will that work ok with the poly primer surfacer underneath?
the epoxy will work great over the poly primer. Spot prime those filler spots with one or two coats; the filler really soaks up the epoxy you spray over it. Since you're going to have filler spots on your car and not a consistent uniform primed surface, it wouldnt be a bad idea to seal the entire car with epoxy then.
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Old 07-21-2013, 09:06 AM
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Lizer is correct, spot priming with Epoxy will work well for you in this case. Epoxy is a very tight primer with rust inhibitors, it will be soaked up by any filler and that is what you want. Apply 2 to 3 coats over your suspect areas, alow it to cure and block sand.

As far as sealer goes, it really is a matter of personal preference, some people like sealer as an insurance coat of product to make sure that they have a uniform substrate. If you have all areas covered with Epoxy or a quality 2K primer and it it is prepped properly with the right grit, there shouldn't be any need for a sealer. Sealers are all about uniform, solid substrates and I will give my rational again. If there is a small repair done on a fender and the repair area is small, say 4" X 4" (I realize that is a real small repair), does the painter seal the whole fender? No, he applies color on the repair area, blends out the color and clears the fender. He wouldn't dream of using a sealer because he wouldn't have any blend room.

Often sealers are used in Body shops because of, as mentioned, suspect substrates and to fill sand scratches...if you have a good substrates, 2K primer or Epoxy, in my opinion there is no need for sealer. If you have done your prep work properly, I find sealer to be another product that you can get dirt in your final paint job.

Yes Dennis, you are right, even 2K primers can absorb moister, that is why it's so important to have a quality Epoxy underneath them. I also like the fact that the poly primer your using is mixed with a scale instead of the little hash lines you get on a tube of liquid hardner for Slick Sand...I always had concerns about that and in the several times I used the product, I erred on the side of caution and ran out of hardner before i ran out of primer...not much...but I did run out.

And Lizer, I don't have a can of Slick Sand to look at but, I did that little search yesterday and wet sanding was OKed...When I was a paint rep, I also remember questioning the Fiberglass Evercoat rep about wet sanding this product. I was told without hesitation that it was fine, and he did go into the rant about resins. I was told that the resins used in Slick Sand where very similar to the resins used in their fiberglass products...that's why they used the same hardner. However, if I ever get into a situation where a customer wants me use this product....for me, I think I'll decline. I'll stick to what I know I can wet sand...I just like the finish of wet sanding compared to dry sanding to much to take chances.

Ray
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