another epoxy primer question
Thread Starter
Instructor
Joined: May 2009
Posts: 121
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From: yardley pa
another epoxy primer question
here is the umpeenth epoxy primer question on the forum. i stripped and sanded my 87 down to bare glass and am now ready to epoxy it. my delemna is, i bought some nason 491-16 epoxy. the tech shhet does not list smc as a substrate. the 491-18 lists smc, but nobody seems to have it. my question is, should i just go ahead and use the nason 491-16?, or should i return it, and try to find somebody in the philadelphia area the carries the spi epoxy? if the answer is use the spi, does anybody know where i may be able to get the spi in the philadelphia, new jersey area? thanks in advance for your help and advice. this forum has help me imensly along the way of this restoration.
Drifting
Joined: Apr 2007
Posts: 1,442
Likes: 87
From: bluff dale tx
here is the best place to get info on spi. all these guys use it. and there's some damn fine gun hands on there. you wont get any google knowledge or bs. they use it every day.
http://spi.forumup.org/index.php?mforum=spi
http://spi.forumup.org/index.php?mforum=spi
Last edited by porchdog; Jul 21, 2009 at 05:39 PM.
Thread Starter
Instructor
Joined: May 2009
Posts: 121
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From: yardley pa
porchdog, i will return the nason. after reading many of your posts and replies about the spi epoxy, i just want to make sure i have all the right info. i will shoot a coat of the epoxy over the bare smc, give it 24 hours to dry and then do any necessary body filler work. give it another 24 hours and then spray another coat of epoxy. correct me if i'm wrong, but i do not need to sand the original coat of epoxy, unless i wait longer than 7 days. after the second coat of epoxy, i will block the entire car and start my basecoat. i think that is all. again, thanks to everyone on this site for all your advice and input.
Drifting
Joined: Apr 2007
Posts: 1,442
Likes: 87
From: bluff dale tx
an overnight cure is plenty. do all you fill work then epoxy again. i use epoxy to surface with. shoot it heavy and let cure overnight or longer then sand. repeat until your happy then start painting.
Drifting
Joined: Apr 2007
Posts: 1,442
Likes: 87
From: bluff dale tx
when a car is new it has a thin layer of primer on it. when i do one i end up painting on the epoxy surface. just like painting on the polyester body. one coat of reduced epoxy as a sealer then color. i do not pile on polyester primer to surface. the thicker it gets the more chance of shrinkage or readout from the surface. my normal on a 50's vette is 6 coats of spi epoxy. each coat cured and sanded. just depends on the condition of the body.
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Drifting
Joined: Oct 2003
Posts: 1,923
Likes: 5
From: San Antonio TX
been there, done that and you will get an outstanding finnish by using the SPI as a surfacer but be prepared to sand a lot. something as small a a small rock chip will take min of 4 coats to cover and the epoxy is much more difficult to block out than normal surfacer. the results are outstanding but just be sure that your end justifys the means.
Drifting
Joined: Apr 2007
Posts: 1,442
Likes: 87
From: bluff dale tx
shoot the epoxy wet and heavy like clear. it shoot have a nice gloss to it. it will build just as good. i use my iwata with the 1.4 and run it wide open and slow. the 57 vette took 6 coats total and there was a lot of repair . you can adjust the way it sands with cure time. first 4 coats cured over night and were wet sanded. the last 2 i let cure a day or so before wet sanding. i don't like a primer that sands easy. it cuts too fast . i like to control what i take off.
Thread Starter
Instructor
Joined: May 2009
Posts: 121
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From: yardley pa
i took the factory black primer off too. i am down to the smc. did i take it too far? on the fenders and some other little parts that are hard to sand, i just wet sanded them with 220. is that rough enough for the epoxy to adhere to? i contacted a spi jobber yesterday and am waiting for a delivery of spi epoxy and some universal clear. hopefully i can start epoxying this weekend.
Drifting
Joined: Oct 2003
Posts: 1,923
Likes: 5
From: San Antonio TX
shoot the epoxy wet and heavy like clear. it shoot have a nice gloss to it. it will build just as good. i use my iwata with the 1.4 and run it wide open and slow. the 57 vette took 6 coats total and there was a lot of repair . you can adjust the way it sands with cure time. first 4 coats cured over night and were wet sanded. the last 2 i let cure a day or so before wet sanding. i don't like a primer that sands easy. it cuts too fast . i like to control what i take off.
with you on all of the above but just pay attention to the bold part, I do all of my sanding by hand and the epoxy is 3 to 4 times as hard to sand. when done it is much better surface to paint on just be prepared to spend more time sanding.
More Than Zero
Racer
Joined: Sep 2008
Posts: 353
Likes: 0
From: West Point MS
So if I go with blocking the epoxy primer, how many coats do I apply before the blocking process? Do I shoot 2 coats, let cure for 24 hours and then shoot 2 more or do all 4 with a 30 min. flash time in between? Do you need to shoot a guide coat or will the epoxy dull as you sand high spots? Thanks for your help.
Safety Car
Joined: Oct 2007
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From: Austin Texas
Corvette of the Year Winner 2017
2016 C3 of Year Finalist
shoot 2 coats of SPI epoxy and start blocking, if you go thru reshoot Epoxy,
the SPI does change color, and works well as a guide coat. 69VETT
the SPI does change color, and works well as a guide coat. 69VETT
Racer
Joined: Jul 2009
Posts: 382
Likes: 1
From: yacolt wa
primer
Epoxy primer is not a fill product.Very hard to sand and sticky.Shoot one or two coats, let dry overnight and shoot two or three wet coats of 2K urethane primer surfacer,let dry couple days and block sand with 150 or 180, use catalysed glazing putty on imperfections,reshoot with 2k until perfect. Guide coat and final sand w/ 600 or 800 wet.
Drifting
Joined: Apr 2007
Posts: 1,442
Likes: 87
From: bluff dale tx
sorry but i disagree. i use spi epoxy only for resurfacing . it sands well and will build and fill much better than urethane primer. plus it will not shrink and die back as urethane does. urethane is the last choice for build. polyester would do much better and epoxy out performs polyester.
Drifting
Joined: Apr 2007
Posts: 1,442
Likes: 87
From: bluff dale tx
die back is the fuzzy spots you find later . urethane is more of a one coat repair primer. everyone gets into this high build thing when it is the worst thing you can do. mill thickness is your enemy. the thicker you get the more solvent pop and shrinkage you will have. the less you have under the color the better.
Racer
Joined: Jul 2009
Posts: 382
Likes: 1
From: yacolt wa
primer vs primer surfacer
Unless you "metal finish" a car body, you will HAVE to provide some type of filler whether it be "mud", glaze, finish putty or surfacer. Epoxy, urethane, or polyester. In the case of a SMC or glass car,sanding it down perfectly w/o some type of "filler" is impossible.
if it is possible, please enlighten me and my appologies in advance.Thanks
if it is possible, please enlighten me and my appologies in advance.Thanks
Burning Brakes
Joined: Jun 2007
Posts: 773
Likes: 213
From: Auburn Ohio
You'll love the SPI and the Porch has got it right- as usual....
Least remaining mill thickness that levels the surface!!! Thinnest under coats WINS!! The thinner remainder has the best chance to exporate carrier solvents.... And least shrinkage potential!!
Longer time between coats the better!!
A couple of weeks in the sun is great... Use Black for best thermal transfer.... Fender Peaks of my 66 in black SPI sitting in direct sun reached 147 degrees last week- Cheap baking booth!!
Porch is the guru... SPI is the best!
Least remaining mill thickness that levels the surface!!! Thinnest under coats WINS!! The thinner remainder has the best chance to exporate carrier solvents.... And least shrinkage potential!!
Longer time between coats the better!!
A couple of weeks in the sun is great... Use Black for best thermal transfer.... Fender Peaks of my 66 in black SPI sitting in direct sun reached 147 degrees last week- Cheap baking booth!!
Porch is the guru... SPI is the best!