sullyman56

Thanks DUB. I haven't bought a gun yet. What size tip would you suggest that would work well with the epoxy and polyester primer? I did see one that had a 1.4 and 1.8 tips. Thanks

DUB

This is where you are 'dancing' all around what you need. The 1.4 for the epoxy seems fine and would work. The 1.8 is just a bit small and may not push out the product enough. This 1.4/1,8 combo is pretty good...But..as I write quite often...TEST, TEST, TEST....so you can get the gun and adjustments and mixes working for you.

You may find that the 1.8 will work BUT you may need to add a little bit of acetone or whatever the manufacturer recommends to slightly thin it so you can apply it. Once again...hard for me to actually 'say'..because I would need to be there to see how it reacts when shot WITHOUT any thinning.

DUB

sullyman56

Not having any experience with this I'll rely on your judgement. I haven't bought a gun and I've seen a number of them come with the smaller tips. I suppose I could get the one that has the 1.4 and 1.8 tips and thin the primer if I need to. I do have some left over body parts from other projects that I can test the gun on. I'll try the masking tape too to see if I can tell how thick it's going on. I certainly appreciate the advice and I'm sure I'll have more questions once I've started.

DUB

Do not hesitate to ask ANY questions.

Just make sure that you clean the gun VERY WELL...SURGICALLY CLEAN when completed.

I know a lot of what I write often times may not be taken seriously. That is fine by me. But those people out there that do this for a living KNOW that much of what I wrote here has merit.

NOT knowing what you are doing or applying is a RECIPE FOR DISASTER!!!! BUT...it is SIMPLE....TEST it and check it BEFORE YOU spray it on your car. And do not THINK for one second that if I am using something NEW...that I do not STOP and take time to test it thoroughly. Depending on what it is...I put it through some serious abuse tests.

DUB

sullyman56

Thanks DUB. I sure appreciate your help. What's your experience with SEM products? The epoxy primer that I'm looking at is SEM metal lock grey. I've never heard anything bad about SEM. Just wondering what you think of it.

porchdog

i use the larger gun for epoxy but i use it differently than most. i let the epoxy induce overnight . this gives it a heavier body to build with. you can turn a 2.3 down but a small gun is limited . especially shooting high builds.

DUB

I have never used the SEM epoxy. I do agree...I rarely hear anything bad about SEM products.

Let me talk to a guy I know who worked for them..I will get back with you.

DUB

porchdog

i use a lot of sem products and like them .

sullyman56

Thanks PD and DUB. Pretty sure it's the product I'm going with.

porchdog

i have never used their epoxy . only the adhesives .
i use spi epoxy .

DUB

Like I wrote...I will talk to my guy and find out what he knows about it.

DUB

sullyman56

I'll wait until I hear what he has to say. Thanks

DUB

OK...talked with the guy I know and he told me that the SEM Metalock is some good stuff and is based on the more current technology of epoxy primers than the PPG stuff.

He said that he would use a 1.8 tip to shoot it. And...much like what 'porchdog' has mentioned in a post I read...my guy says you can apply several coats in it and not ahve to apply any pother primer. This epoxy primer is a high build and sand-able but does has that very very thin tacky layer that you have to get past when sanding. I think 'tacky' may not be the right word...but the epoxy will want to slight clog your paper while you are getting past it.

I would still talk with SEM tech department and ask them the capabilities of it. It does seem like a good choice to use.

DUB

sullyman56

Thanks DUB. That's the product I'll be going with then. How much primer should I buy? I don't suppose 1 gallon will be enough.

DUB

I believe that guy I know said that is is mixed 4:1:1. Maybe a gallon will do. I can not say for sure. You might want to get some more for testing.

I would highly advise you calling SEM and talk with them .. I do it often and they are really helpful when I have some odd adhesive issues to see if they offer something that will bond what I am repairing.

AS I have written before...I would advise you in mixing some and testing it out so you can get it dialed in...before you primer the body. Going in with a product you have NEVER used and HOPING all goes well is really RISKY. Once again...if you do...and you have a problem with it. You will WISH you could turn back time and do it all over again and practice and test first...because the amount of time to get things prepped again and do it all over will BLOW YOUR MIND.

DUB

sullyman56

Thanks for the good advice. I have some old body parts to test the primer on. I'll try a gallon and see if that's enough. I think four coats would probably be ok from what I've read. I know how much work is involved since I spent so much time sanding and prepping the car for the primer. I'm not a big fan of doing things more than once so I'll heed your advice on this. Another question. Do I need to sand between coats or wait until I'm finished applying the primer?

DUB

It depends on how well your bodywork turns out. Because when you go and spray it...it can show up issues that you did not 'feel'....but now can see.

You will need to 'wrap your head around' the possibility that you have to prime it more than once.

SO...depending on what SEM tells you. When you apply their epoxy primer....I do not know if it is a 'wet-on-wet' type of primer. Meaning that when the primer is shot...it has a 'window' of time that allows another product to be applied on it and NOT needing to be sanded.

The concern I have is the epoxy I use does not build like what I gather the SEM epoxy does. This is not bad...but it would be where I would need to have in intense conversation with the SEM tech rep and ask numerous questions. Because if I am going to be applying a polyester primer afterwards...I would have to take into consideration the film build of the SEM epoxy.

But sanding between each coat is something I honestly feel you do not need to do. Get some material on it and depending on how it looks would 'tell' me that I need to block it and apply more epoxy...or go to polyester primer.

So much depends on if it is a wet-on wet primer or can be applied and allow this....and IF you thin it down enough to get a good coat to 'lay down' on it that will cure correctly but due to the thinning... the coat is not building as much...because you plan on the build up for blocking being in the polyester primer.

DUB

sullyman56

Thanks DUB. I'll be sure and talk with the tech people at SEM before I spray it. As to sanding, am I correct in thinking of using a fine grit paper such as 320 or 400?

DUB

I do not know what you are referring to...if the 320 or 400 grit is what you sand the body with BEFORE you apply the SEM epoxy...or AFTER it was applied.

I know I would not have the body sanded that smooth before I apply an epoxy primer that has the build that this type of epoxy has. It is thick and can cover 180 grit rather easily...as I was told. AND the open hatch of the 180 grit sandpaper scratches actually works better due to allowing a thicker product to fill them IN ...instead of COVERING OVER THEM.

Using 320 or 400 grit to sand the epoxy....Not necessarily....because if you are going to put polyester primer on top of it...you can get way with 180 or 220....or what you do then is call and ask the company of the polyester primer you plan on using would LIKE to see as a prepped surface in regards to grit.

Talking with SEM's tech line can answer so many questions....such as being a 'wet on wet' scenario...so NO sanding is required....due to applying the polyester over it. Or the ability to thin it and make ti not so thick of a coat, etc.... So ..asking these questions can be a mute point all together...kinda like a 'cart before the horse' scenario.

If you can find a way NOT to have to sand the body between applications of different products because they will adhere to each other and allow this due to chemical adhesion.....I DO IT.

Here is an example that you can easily understand, When you sand a surface it gets scratched. And if you look at these scratches from the side cut away view....24 grit would look like the side view of a two man buck saw used back in the day to cut down a Redwood tree. The grooves in the teeth are DEEP and wide. If you sand a surface with 1000 grit for example....the side view of this under magnification might look like the side view of a 18 tooth hacksaw blade...where the teeth are close together and the grooves are shallow.

SO...when a product is being a sprayed...often times the consistency or viscosity being thick. Scratches that are NOT shallow and close often times work better due to the product can flow into these groves and scratches. if they are shallow scratches ...the product will cover over them and can...trap air and moisture and show up when the panel gets hot. Many variables come into play here where this comment can be contradicted....such as adding thinner or reducer to allow the product to flow better, etc.

DUB



DUB

sullyman56

I sanded the entire body with 180 previously since it is new fiberglass. I should have mentioned that before. I was asking about sanding after spraying the primer. Do you recommend spraying the epoxy and then polyester primer? If that's the case I'll be buying some of each instead of just the epoxy. Maybe I'm wrong, but I thought that I would have to sand the primer to prepare for painting. Please correct me if I'm wrong about this. Just want to make sure I do it right.