2k primer shrinkage

S

ShaunD

i am working on my 1979 piece of crap trans am. it is coming along fine thanks to all of the advice from you folks. i appreciate you helping me out. I started by cutting out all of the rusted metal and then replacing it with steel welded in. i then coated everything with spi epoxy and then did the major fill work. i have then sprayed spi 2k regular build over that and have blocked it down and filled in the low spots with icing and sanded them flat.
The question is do i have to worry about shrinkage with the spi 2k regular build. i dont want to bust but and then come back in 6 months and have scratches and stuff show up. what is the key to not have shrinkage? is there a certain amount of time you have to wait before top coating or something. i have it blocked to 150 grit right now using the 2k.
would switching to a product like a polyprimer for the remainder of the blocking process help or cure any possible shrikage? Featherfill would that be the product to use
The second question is about guide coat. I have 2 colors of 2k primer. how much can I thin the 2k color that I am using for my guidecoat as i want it to go on real thin
 
Shaun, here is my take.. So take it for what its worth..

All 2k products shrink.. Even our epoxy and clear.. They shrink as they cure,, Just a fact.. What you are asking, is how can I prevent any noticeable shrinkage over the long haul..

For the most part with any of these products it is time and the largest "helper" we have is the Sun and its UV rays.. That will do more for your filler all the way to clear than anything.. While I do understand that fillers cure with heat, it still applies, just as not as greatly as our ISO counterparts..

Im going to answer this in a couple post to break it up slightly instead of having a page of info you may tire of reading..
 
Please note my times that I offer will not be those for a shop trying to make profit or for a dealership trying to turn and burn.. These times apply to those like myself, who do not have to rush any of the work they do to try and get the best finish possible..

So here goes..

If you live in the South like I do, I think that is even better where sun and heat are invovled..

After your 2 coats of epoxy.. I think you should wait a couple of days before you touch the car.. As epoxy cures it gains adhesion.. I cant tell you how many times someone has written on the forums.. I sprayed my epoxy yesterday, spread filler today.. and I can scrape off the epoxy with my fingernail and its not feathering like it should..
Epoxy is a slow duck as Barry once put it, and I could not say it any better..

Lesson... Give your 2 coat non reduced epoxy a couple of days before you start covering it with filler.. You can even give it a slight scuff if it appeases your mind before filler application.. Some prefer to do this, even though it does not have to be done.

Sun exposure: If you have the ability set the vehicle outside for 1 full day.. this is as good or better than it setting inside untouched for 2 weeks.

Rough Blocking.. If you need allot of blocking to straighten your car, then I highly suggest the use of a polyester primer.. It does not shrink as much as the 2k primers we use, regardless of whom makes them.. Remember some things are beyond any control ( shrinkage ).
Once you have your car straight with polyester, then move onto a 2k for your final blocking..


Barry taught me something about blocking in general that I think is imperative..
If you dont block thru and hit metal and your filler work, then you have not blocked enough.. This applies to your polyester blocking in this instance or 2k if you only used 2k

Lesson: Use polyester for major blocking if panels are wavy after your initial bodywork.. Start with 80 grit or 150.. No higher grit for blocking this product in my opinion.

Sun exposure: I like setting my poly sprayed cars in the sun for at least a day before I spray 2k over them, or spray more polyester over them.. Even after they have been blocked..

If you are ready for 2k.. Take a DA with a soft interface pad and 220-320 and buzz over your 150 scratches to knock the hard edges off and smooth it down a smidge..
Some think you dont need to do this, while many others argue its a must..
I have not always done that, however I have had primer scratches show back up over a couple of summers when I did not knock down those hard edges.
To me its cheap and fast insurance.. Do as you like
 
Flash times as Barry pointed out above as I was typing..

I took that for granted.. Thank You Barry for reminding me!!!

Yes Flash times are critical.. The longer the better for most everything.. Solvents are the enemy so to speak.. So the longer we can go and allow solvents to flash out then the better.. This helps with the dreaded shrinkage you are speaking of:cool:

30 minutes between coats of primer is excessive, but doesnt hurt..

I know some guys go an hour on epoxy between each coat
 
2K Primer

2K primer is your next step.. As I pointed out in the above post.. If a great deal of blocking was needed even after your filler work, then I strongly believe that poly is better suited for this..

If you did not want to use poly, then I would suggest you re-work your bodywork until you have it straighter/flatter etc.. Then a 2k would be just fine..


Final Blocking:.. As with blocking thru to metal and filler.. I suggest you block thru your 2k and hit the poly good also..
I start with 150 grit here also..

I spray 3 coats and block with 150.. I will do this until it blocks out perfect without breaking thru to ensure straightness.. Then and only then will I spray my final coat of 2k..

Final 2k: Spray your 2k nice and slick, this will make this last blocking session easier.. You can also reduce the last coat to aide in this..
I block this coat with 320.. Some like to use 400.. But I use 320.. I think it cuts much better and makes for a better job in the end..

Sun exposure:I like to let the car set outside again for a couple days.. Then I wash it really good with something like Dawn dish detergent to make sure I get it nice and clean..

At this point you will need to re mask for your sealer, base coat or single stage urethane, whatever the case may be..
 
There are a couple of ways you can seal up the 2k.. Use a dedicated 2k sealer which spi sells one.. Or you can use epoxy..

If you are using a dedicated 2k sealer, then you will seal and base within a half hour to hour..

If you are using epoxy, then its a different process.. Many reserve epoxy as a sealer for show work only.. I figure if time is not an issue and you are trying to do the best job, this will be your choice.. However you can still lay a gorgeous paint job using a dedicated 2k sealer...

Epoxy as your sealer: I would induce the epoxy the night before and reduce it 20% before you spray it the next day if time and memory allows.. Sometimes you will just not think to induce and it will be just fine if you dont!!

Lay 2 wet coats with 20% reduction and then once again,. I let it bake in the sun for the rest of the day after it was sprayed in the morning

Wet sand the epoxy with 600.. This will make for a nice smooth finish for your topcoat to be applied over.

Beyond this you will be splitting hairs over processes.. Some guys will wet sand the base with 1000 and re apply base before clear.. There are allot of different ways people do show work..
 
I hope this helps.. I have been correcting my children in the process of typing this, so I may have left something out or missed something..


Please feel free to correct or make any additions to what I posted for this person. I am by no means the Authority on paint, I was simply trying to help this along..

Happy Fathers Day!!
 
Induce night b4 and reduce it once ur ready to spray it and having first thoroughly stirred it back together then add in the reducer
 
For no particular reason, I have always mixed the reducer and everything all at the same time. I haven't had a problem that I know of. Is doing it this way a bad idea? The tech sheet doesn't reallly say either way from what I remember.
 
No my man, wont hurt a thing.. Just the way Barry told me to do it long time ago..

The things I speak of are from experience and from what Barry has taught me..

You wont find me telling you to do things with products I have not done myself!

Honestly I dont induce the epoxy.. I didnt induce it when it had a much greater viscosity and many people complained about it.. I liked it better thicker, but I was not the majority in that regard!!
 
to this point I did my initial spray over bare metal with spi epoxy. i then filled in all the low spots with evercoats rage extreme and the small spots with icing. I flattened the high spots with my body hammer and then blocked it all flat with 80 grit. I then resealed all of the filler and sand throughs with epoxy. then I sprayed 3 coats of spi 2k regular build primer and then 1 thin coat of spi 2k primer in another color to use as my guide. I allowed at least 1 hr between coats of 2k. it sat overnight before I got a chance to block it out. I filled in the minor lows with icing. right now it looks and feels really straight. to this point this process has taken me around 6 months to complete as I have a job, wife and kids so I dont get much time to work on it. I allow more than recommended between coats. to this point I have not used any poly primer just spi epoxy and 2k primer only. its blocking pretty smooth with the 2k at 150 grit. i guess if I was earlier in the process I would of used poly but at this point it is blocking pretty straight with minimal sand thrus. does this sound right. I will have to throw the wheels back on it on it and take it off the blocks and get it outside so it can set in the sun for a few days. So its ok to do just 2k but poly probably would of been a better choice if starting over being as the 79 bird was pretty dented up. again i am in no hurry so time is on my side. taking it off the blocks and moving it outside is going to be a pain in the butt though.

once 150 is blocking straight I should shoot on a couple of coats and then I can move to blocking with 320 and then 600 correct. Thanks again for all of your help. being a total rookie I need to ask a ton of questions to make sure I am on the right track
 
I don't even have kids and mine has taken over three years at this point. So, you're doing pretty good. If you think its good with the 150, I would spray a nice wet coat of straight epoxy on it. Really check the car out using the shine of the epoxy. Then block the shine off the epoxy with a finer grit...maybe 320, you'll have to be the judge of that. If you have shiney low spots giving some trouble, go coarser, don't push harder.
 
well yesterday on fathers day my wife gave birth to our second child!!! so my plans are going to be a little slow with my car for a bit. i am sure i might find a minute here or there but am not counting on much. hopefully i can get it painted by the end of the summer. heck i am in the hospital right now with my new daughter and my wife as i type this. What a great fathers day present.
 
take your time.

Me and my wife go in the morning at 5:00 for them induce her for our 2nd child(we have a 5 year old Boy)this time we are getting a Girl.

nothing better than a present like that imo for Fathers Day!!!!!!!!

they will and do throw a wrench in the projects sometimes but it all works out in the end.



you will be fine with all 2k i have done some really nice all overs with it.sure it shrinks worse than Poly and Epoxy,but it will still look good in the end and its taking this long it should have plenty of time for everything to set-up.

Best of luck Travis...
 
Congrats on the kids to both of you.. If you read in my post you will see i said you need to break thru.. If you were not breaking thru to metal and filler on your first round of 2k with 150, then I would be concerned it would not be straight/flat as it could be, but then again it may be straight/flat, depends on how you did blocking.. You will have to be the judge of your work here my friend..

Let me say this..

Before you move onto stepping up the grit to 320.. That car needs to be dead on the money.. Then and only then should you switch to higher grits.. I have used only 2k before and went thru 3 blocking sessions of 2k primer at the 150 mark until it was right.. Then I sprayed 3 more coats of 2k and blocked it with 320 before my sealer..

You will block and block and block.. I think that is the major difference in a good job vs a great job..

Enjoy your kids guys and put that car in the sun for a couple of days and let it shrink some more.. Wont hurt a thing.. Also wont hurt to block it again with 150 after it sets outside if your unsure about it being right on the money

Hope this helps..

Happy blocking
 
Thanks for the congrats and the advice. I think i will let it set in the sun (whenever we get some more!) and then shoot some 2k and reblock with 150 just to be safe. Right now it looks and feels pretty darn straight but again this is my first time doing this so my skills are not honed by any stretch. I am in no hurry and I want this thing to be nice and straight. I wish i had understood what poly primer was used for before starting as it would of saved me a ton of time getting everything straight! panels on a 30 year old vehicle are not the straightest and most dent free things you would want to see! overall its been a very interesting and learning epxerience
 
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