Paint Preparation Questions

That is an easy answer.

Depends on how fast you are working.

Shops always go direct to metal cause it is faster. The shops also are putting paint on the same day and will protect the metal.

If you are working slow the epoxy first may be better as the metal is now protected.

Best I can find the best adhesion comes from laying epoxy down first then bondo on during the recoat window when the surface is still 'open'. The is after a talk with the owner of SPI and a discussion of how the products work.

From what I have gathered people often sand with the wrong grit paper for the product they are using. With proper sanding or other means to make the correct rough surface either product will adhere quite tightly to the surface. My favorite is the ones who think 40 grit is best. It has too few scratch per inch which means more flat areas the bondo can not grab onto. It is best to use the high grit that is recommended for more scratch per inch.

Both products will not cure at the surface if it is acid. So use acid products with great care as the surface must be neutralized or it will not be sticking at the surface.

The above comments are based in facts, not opinion, as best I could dig them up over the years. So feel free to go look it up for yourself.

I KNOW the facts.

I don't have to look them up, I have been laying filler on bare metal for decades and will continue to do so.

I don't need any biased opinions from paint sellers that tell you to lay bondo over their product just to sell you more.

I can never figure when some lay epoxy down then filler, then how do they ever feather the filler without digging the edge of the epoxy.

You have two materials of different hardness .

I have been blasting off material for decades and have never seen rust under filler, that was not an obvious lousy filler/repair job in the first place.

This site sums it all up....

http://www.autobodystore.com/filler_&_epoxy.shtml

But it is your car and you can do anything you want with it, but let the OP decide what he wants himself by reading the FACTS, not having stuff rammed at him just because someone does that themselves , and has not gone the extra mile like this guy has to prove his methods .
 
I didn't read every post in detail in this thread but I have used lacquer based paints for 40+ yrs. They are forgiving to someone who is not a professional painter, runs can be repaired easily & later repairs blend in well. I have also used DuPont Centari & base coat clear coats. What ever paint is used one thing that is important is to clean out the seams especially around raised moldings like found on Model A's & other older cars. I have seen too many nice paint jobs bubble up or blister in these areas because sanding dust or other contaminates were not cleaned from these areas. Use a brush & clean these areas well before applying any paint.
 
lacquer will not stand up to acid rain, bird droppings, etc etc.

Lacquer is a reversible process. ie when dry, take a rag wet with lacquer thinner and you can wipe your paint right off, whether new or old paint.

If a Model A is to be painted correctly the fenders should be off the car at the very least, and best if the doors, running boards, and aprons were all off as well. This will avoid the contamination you mention in the seams
 
Bergy,

My advice is to see if your local community college offers an automotive painting class. I was lucky in that a friend suggested I take this course and a local community college offered it once a week for three hours for 14 weeks. Before taking this class I had only painted using spray cans. The course will teach you the basics and provide the spray booth and paint. We were all required to purchase cheap Harbor Freight HVLP spray guns. After the 14 week class I started to paint small chassis parts and continued to improve my skills. I bought better spray equipment and built a home made paint booth. I made many many mistakes along the way but I stayed at it. The end result was a Henry winner that received full points on paint. I painted it all except the pin stripe (that was done by Jim Brand). Although a significant time investment, such a course will save you time in the long run. I used all PPG products and used PPG Concept as my top coat.

Best of luck - Hunter
 
I KNOW the facts.

I don't have to look them up, I have been laying filler on bare metal for decades and will continue to do so.


But it is your car and you can do anything you want with it, but let the OP decide what he wants himself by reading the FACTS, not having stuff rammed at him just because someone does that themselves , and has not gone the extra mile like this guy has to prove his methods .

Now only if you will read what I said maybe you would not have been so rude. There is a reason why people walk away from these forums.

In summary of my previous post, both ways work fine if you use proper scratch as per the manufacturers directions.

A hobbiest might be better off laying down epoxy to protect the metal. This depends on how fast they are working their metal. Some go for decades between bare metal and finish paint.

A person, the owner of SPI, who manufactures paint told me that the best adhesion is epoxy to metal and bondo to epoxy during the recoat window.

I am fully aware of the testing done on autobodystore.com. While interesting I feel the testing is not fully valid. Quite frankly that was a few years ago and forget the reasons why I did not feel the tests were applicable. I put more weight on a direct discussion on the chemistry and physics of the two systems with the owner of a company that makes this stuff for a living.

So where did I "ram it down your throat" that you should always put bondo on epoxy?

I am only trying to present facts so people can make informed decisions as to how they might approach their restoration. Each person may have to take a different path depending on their situation.

I personally have done both. I am also aware of the hardness differences while sanding and did not think to add that point.

Please try to be constructive with comments in the future. I am very open to any evidence based discussions as the idea is to present valid knowledge and try to help all in improving their skills.
 
Wow, lots of stuff, thanks. Brent thanks for the summarizing my situation so well -" lets keep it simple for the beginner"...

I reached the conclusion to not use lacquer long ago, but thanks for all the discussion and education.

I picked up on a couple new topics in the discussion I'd appreciate a clarification on - zip strip residue removal & the bondo debate.

I had planned to wipe down the metal with a wax/grease remover after zip stripping & wire brushing/sanding to bare metal, prior to epoxy primer. Is there something else I should be doing to get rid of zip strip residue? Someone mentioned hot water wash when finished getting to bare metal, which I assume needs to be dried good to avoid rusting.

I had planned to do body filling/bondo (minimal as I can) after epoxy primer, within the 7 day recommended working window. Is this the wrong thing to do? If this is not the correct thing to do, I would have to ask again why I would go through the bother of removing the existing bondo to get back to bare metal (basis of my original question).

I note the mention of PPG Concepts line for the single stage urethane paint. My local PPG supplier had suggested the "Shop Line" products stating they're as good as Concepts product and slightly cheaper. Comments and Experiences?

Thanks again
 
OK, I checked with a source and he said that if you used paint stripper with the car assembled, after you wipe off as much of the gunk as you can to wash the panels down with lacquer thinner. But in this case the residue has already dried. I'd use lacquer thinner anyway.

If the panels were removed from the car they could have been hosed down with water which is the customary procedure when u use stripper; then lacquer thinner.

I would grab an old fender or chunk of sheet metal and apply stripper and wipe as you did and let the residue dry and re-wipe with lacquer thinner and apply the epoxy you have in mind and test for adhesion.

We try to avoid the chemical complication of stripper.

I would take the extra step of using phosphoric acid as a wash (Ospho is one brand) over the bare metal after washing down with lacquer thinner. We always do this in our shop. If you do, do NOT wash the phosphoric acid off with water, just wipe it down and let it air dry. I have posted extensively on this forum about this, so use the search function to spare me the typing, and I always trigger a flood of naysayers that say this will cause nuclear destruction, sterility, world war, famine, etc etc. So you will have to be your own judge. However,the process is called 'passivation' and is well documented in the metallurgy books. And, if you failed to take this step in the very humid northeast, which I have gladly left behind, your paint would begin to fail in 5 yrs.

We always remove all old bondo, and typically find some rust underneath some of it. There are a lot of wannabe paint and bodymen out there who have some odd ideas of what to do with bondo, so beware unless you remove it all. We have found old foil gum wrappers, old pieces of window screen, etc embedded in old bondo.

As far as epoxy, get your metal as clean as can be, use Ospho as described in earlier posts, scuff with red scotch brite from an automotive paint supply house (buy an entire box, you are about to use a bunch of it), wipe down with pre-cleaner what you call wax and grease remover, and shoot your epoxy. Let cure 2 days. Start applying your bondo (Rage is one very good brand, forget the cheap stuff you find in automotive parts stores, they sand like rocks). Don't worry about any time window. In fact even if we can get bondo on there right after the 2 day cure period, we always scuff with red scotch brite. If you scuff, you can apply the bondo anytime you want. Once the bondo has all been blocked, you are gonna apply another coat of epoxy anyway, to answer the question an earlier responder brought up about scratching thru the first layer.

There is way way more to body and paint than you can possibly imagine, and it all involves pricey material, especially your color coat.

I have never heard of Shop Line, only Omni which I thought was their second line. But we shot Omni once for a customer who wanted it and it is a totally crap product, and we will never use it again. We use only Concept or PPG base/ 2021 clear.

I hate to do all this typing because invariably someone is gonna get on here and criticize everything I have written, despite that Miles and I have painted a boatload of cars with never one failure and despite that he went to restoration college at McPherson Kansas and knows more about all aspects of resto than most people 3 times his age.

So, If you have your own way of doing things, keep at it, and rag on someone else. Let the OP try to absorb as much as he can to get him to keep asking questions about the issues and maybe in the meantime he can find a night class in how to do this. There are such classes out there

Oh, and remove any and all silicone products from your shop/garage NOW else be ready to do the whole mess all over, since even storing them in your shop will cause fisheye later. I am talking about that tire shine crap and anything else with silicone in it
 
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