KP-21 Epoxy primer question

[tiller2nv]

Ive always used Dupont fill and sand primer. I thought I would give the HOK KP-21 a try. Ive seen some tech sheets on it and it says to sand with 80 grit dry! This seems corse! Im use to hitting the part with 220 and then shooting the Dupont. Is this right for this primer?

 

[myfamiliacc]

When it comes to House of Kolor, always trust the tech sheets. Spray it on, then sand it flat with 80 grit /ubbthreads/images/graemlins/agree.gif, some how this helps blend in any bodywork. Afterwards just use regular primer, sand with 400 grit and your are ready for sealer or paint.

 

[Gunner]

Hmmm...I'm just about to start my project with HOK. Having you say 'follow the tech sheets' is good, since that improves confidence that I'm not missing some little secret. But then you say to prime after the KP-21 when the tech sheet says that you can go to the KO-SEAL II after the epoxy primer.

Gunner

 

[Bornhard]

I'm still covered in some KP-21 dust. What an f-ing day! I had a couple sets primed in that stuff today and did some sanding.
When I put the first coat of KP-21 down, I let dry for how many ever hours it takes in the temp. you're in. I put a guide coat of black down and lightly sand with 80-120 grit paper to see where the trouble areas are. Then I get the putty out and do my putty work. I let that dry and sand those putty spots again with the 80-120 grit. After I like how the putty looks and feels, I put 3-5 coats on in thin-med. coats. Once the primer is dry to the touch I put the parts under a heat lamp, or in the sun. Usually I wait till the next day to sand the primer smooth with 220 grit. I don't like rush the sanding process, though I did today, sanding 4-5 hours after spraying, the edge of the sandpaper dug into the still semi soft primer a little bit. After that I put a sealer on it, if there's no need to put another thin coat of epoxy primer on. The sealer does a great job making the surface smooth for painting. If there's any probs in the sealer I use 320-400 grit on the problem areas.

Please let me know how you like that Dupont fill & sand primer. Are you using the Acrylic stuff, or the catalized fill & sand version? I use Dupont & HoK products everyday. I got away from Dupont Epoxy, & switched to KP-21. Real happy with it. There's a bodyshop guy up the street that swears by the Acrylic Dupont fill and sand primer. He puts down some epoxy and sands it with 80 grit. After that he puts a few coats of Fill and Sand over it and sands it silky smooth. He showed me the results and things look good, just unsure of the durability of the product. After he sands the fill and sand smooth (easy sanding product) he seals it and it makes an excellent painting surface! I looked into the catalyzed Dupont fill and sand product and was curious about it, but I believe it cost over $200 for a gallon and the activator. To me HoK is an excellent product and cheaper to use /ubbthreads/images/graemlins/sunglass.gif

 

[tiller2nv]

Im using the Dupont that you add thinner to and thats it! This was my first go with the HOK stuff and all I can say is Im done witn it! The dupont is cheaper and will sand within a hour! I take 500 wet to it and its as smooth as silk! The HOK takes too long to dry. Ive been talking to a buddy of mine and he said dont waste your time with the HOK primer and sealer. Hes a old school guy. But I thought I would give it a shot, turns out he was right! /ubbthreads/images/graemlins/foreheadslap.gif

 

[Bornhard]

That's the Dupont Acylic Laquer Fill & Sand primer. Do you spray that directly to metal? Does it adhere well & is it durable?
It does sand easily and within 30 minutes after spraying. You should still spray a sealer over it (Nason or Dupont).
That's straight out of the Dupont Paint Tech Manual.

That acrylic primer is about $110 a gallon and then you have to get some thinner, $20-$30. I paid a little less for KP-21 epoxy primer and I feel it's better to put epoxy directly to metal etc. I don't think that's a waste of time to make sure your paint stays on the metal. Hey Rex, you should have some input on this subject (read bellow) /ubbthreads/images/graemlins/haha.gif <font color="blue"> </font>

 

[rex]

/ubbthreads/images/graemlins/haha.gifJoe,has the putty been sticking good to the HOK epoxy?I wasnt sure how it would work.You're right on using it on steel.If you're going to use lacquer primer (you know my view on that) make sure you investigate the proper sealer to get adhesion from the primer surfacer up to the base,those lacquer products are slowly being weeded out and replaced.I won't go into the other drawbacks now.

For anyone reading this but Joe-DON'T USE LACQUER PRIMER OVER BARE F*&#@&G STEEL! I can 99% guarrantee it will bite you in the ass on a job and cost you a redo!This is too much work and expense to gamble on that 1%.And ,if you used the red oxide I put those same percentages on it blistering twice as fast as any problems you'll have with the grey.It won't fail until down the road and after any warrantee anyone gives is up,but that's a mark against you when they find out the problem.I'll stand behind my paintwork for years with the exception being checking on overly thick work or natural fading.It won't rust under my work and it isn't coming off.If it does you have a free paintjob at my expense and I don't like that idea one bit.

 

[Bornhard]

Rex, what'cha sticking your putty too? I've applied basecoat/clearcoat putty over epoxy primer for a little over a year now and I believe things are working out well. I've banged, bashed and harshly sanded on the putty applied over the primer and it's not going anywhere, so I would assume it's staying. Kosmoski talks about applying putty/bondo to his primer and covering it with his primer.

He's a trip to discuss custom painting with!!! Ooh man... /ubbthreads/images/graemlins/freak.gif

 

[rex]

Cool,I figured HOK's was cool but wasn't sure.I use PPG's DP epoxy.Sounds like that stuff dries faster though,I'll have to try some if I can get myself to change.I'm bad about replacing something I know is good and works.Never met Jon but hope to someday.

 

[tiller2nv]

Well as some of you know Im still learning this great hobby. Ive shot a few parts and used the Dupont. I do sportbikes, most of the parts are plastic and it works well for me. But Ive also used it on the tanks without a problem. The thing that ticked me off about the HOK it the tech sheet sait to scuff the part with 80 grit. I thought this was a bit much but I followed the tech. BIG mistake! I have a tail section that has some DEEP scratches!! I dont really know what to do with at this point. Do I sand with 220 wet untill they are gone? The said part is I felt as though I was getting really good at this untill I hit this snag!

 

[Bornhard]

I talked to a Dupont person about all of this and the said that you can put the epoxy directly on the metal, sand away, then put on that fill & sand to smooth out the surface. Seal it afterwards and then spray.

If I have deep scratch marks in my epoxy I started to skim it with Evercoat putty (thanks Rex) and then sand that stuff smooth...put some sealer over it. HoK says to use more epoxy over putty, but to me that's back to square one with more sanding involved. If the sealer looks good, time to start painting.

All this primer stuff gives me a headache though (I mean thinking about the stuff, not breathing it!)

 

[John Pierce]

If you are painting plastic, you don't need to use the HOK epoxy at all, you can just use the primer/sealer after you have sanded the plastic with 220 to 400 grit. You could use the epoxy if you want, but it won't really get you anything more than just the primer/sealer on plastic. I've painted quite a few plastic parts with HOK primer/sealer underneath and have no retention problems.

When the HOK book says sand with 80 grit before the epoxy, they are talking about on bare metal and that is correct. You will not have the deep scratches you are talking about on bare metal.

JP

 

[tiller2nv]

[ QUOTE ]
If you are painting plastic, you don't need to use the HOK epoxy at all, you can just use the primer/sealer after you have sanded the plastic with 220 to 400 grit. You could use the epoxy if you want, but it won't really get you anything more than just the primer/sealer on plastic. I've painted quite a few plastic parts with HOK primer/sealer underneath and have no retention problems.

When the HOK book says sand with 80 grit before the epoxy, they are talking about on bare metal and that is correct. You will not have the deep scratches you are talking about on bare metal.

JP

[/ QUOTE ]
The reason I was using the primer was to get a good grey down. I found that the HOK silver sealer doesnt really hide very well and If i start with a grey primer it works great! Looks like I learned something again from this board! After I used 80 on the tail I said no more and went on to the fairings and used a 400. That ended up working out great! Well looks like I have a lot of sanding on this tail to do! /ubbthreads/images/graemlins/foreheadslap.gif

 

[Bornhard]

I shot some KP-21 yesterday and first thing this morning I sanded it all with 120 grit. The stuff is tough and that paper slightly scuffed it. After that I sprayed some Ko-Seal white over it and things looked great. I had 2-3 spots I had to sand and I used 220. Next was another coat of Ko-Seal and I'm just gonna let that sit over night (it was getting late for me).

Things look real smooth & that ko-seal fills the sand marks.
Drys within an hour too I think, never timed it.

Oh the 80 grit deal, not real sure about sanding the primer with that unless you have bad spots and then you put some more primer over it, but you should prep the bare steel with 80 grit before priming. /ubbthreads/images/graemlins/cheers.gif <<<need one of these drinking a beer /ubbthreads/images/graemlins/cool.gif