First time painter here, working on a 66 Mustang. I'm afraid I may have messed up last night and I'm not sure where to go from here. So far I have been working on the dark areas of the car: engine bay, interior, trunk, etc.

At this point the car has been through these processes:

Rage Gold Body
Matrix Epoxy paint
Matrix 2k High Build Urethane
Sanded w/ 400 grit wet

Here's where things get messy. Last night I was set to start shooting my top coat, a single stage of SEM Hot Rod Black. In preparation I planned to shoot a reduced coat of the Matrix Epoxy as a sealer. I had a little left in an old gallon, so I had picked up a fresh one ahead of time.

I mixed and shot the engine bay and half the interior. Mixed up another batch, 1/3 old gallon, 2/3 new gallon. Finished the interior and started in on the trunk. Mixed up another small batch of the new gallon, finished spraying the trunk. As I was finishing, a cold front was moving in, bringing snow. Now I was in a semi heated garage, so I thought no problem. After an hour or so, most of the car had dried as expected, except for the area in the trunk that I had sprayed with the new gallon.

Thinking it was weather related, I decided to let it cure over night and top coat in the morning. Go out today and it's hardened up a bit, but is glossy than the rest and I can still dig into it with a finger nail.

After much Googling, two answers seem to pop up: weather and mixture. To make sure it was the weather, I go double check my products/ratios. This is when I find out the the paint store sold me the wrong gallon and hardener. Grrr....

Turns out Matrix has two different black epoxy primers, MP900 (which is what I had been using) and MP470 (the new gallon). Not only do these primers mix at different ratios, but the hardener is a different product number as well.

The product specifics are as follows:
MP900 - 4:1:2 (as a sealer) Hardener is MAV-420
MP470 - 1:1 (no specifics for mixing as a sealer) Hardener is MAV-465

Last night I sprayed three cups:
1. Properly mixed MP900
2. 1/3 MP900, 2/3 MP470, right hardener for the 900, wrong hardener for the 470. Wrong mixture for the 470 as it was done 4:1:2 instead of 1:1
3. MP470, mixed wrong at 4:1:2 with the wrong hardener

Now the paint store sold me the wrong paint and hardener (mismatched). I'm not sure how pissed I should be about that (because I should have checked the numbers before I started mixing, but I assumed the paint store knew what they were doing). Clearly they messed up, not selling me a matched primer and hardener.

But beyond that, I'm not sure where to go from here. The engine bay and interior seem to have dried well, producing a solid dull black. There are one or two smaller, slightly glossy spots. Not sure what to do about those.

The trunk is still glossy and soft. I'm not sure that it will ever harden given that it was completely the wrong ratio AND the wrong hardener for the product. If it won't ever harden, do I need to worry about the areas that were spayed half and half?

I've been busting my butt trying to get this done and looking really good. I was super disheartened when I saw the wrong numbers on that gallon this morning. So experienced painters, what do I do and where do I go from here?

First, call the manufacturer and talk to the tech guys. Explain what has happened and ask their advice.

They may have a solution that will set the epoxy or it may be ok after a longer period or, worst case, you'll have to strip it off and start again.

You will get much better advice there than here since they are the ones who know the chemical composition of their products.

Once the solution is worked out I'd then be marching down to the local distributor and asking for free replacement product.

real good advice above, call the manufacture. epoxy will go dormant at temps below about 55deg and above that to about 65 it will slow down considerably. beings that it is starting to harden see if you can put some type of heat in the trunk area to get the temp up to around 70-75, it may take a few days. most epoxys are quite forgiving on mix ratios, they will still work it just takes longer.
Jay D.

strip it off, period. 5 gallons of lacquer thinner. start over.

yes your jobber may have sold you wrong hardener but they did not pour it into your paint.
learn to read tech sheets and double check products. 100% your fault the minute you mixed.

don't mean to sound harsh buddy but that's the way it is.

AND ANOTHER This is for sure what I would do if it was a customers car. its up to you what you do with your car. if its just the inside of the trunk I would try the heat first and see what happens. yea, I don't know if I would get to huffy with the jobber you should have checked everything you were mixing. I think everyone has probably done this, usually you only do it once. get in the habit of reading your info sheets and checking your materials. I even go so far as to set the cans of one product on different sides of my mixing bench so I don't grab the wrong can by accident.
Jay D.

I keep a binder for all my tech sheets, then I write notes and use a yellow highlighter on mix ratios, pot life etc.

I also use a sharpie on the cans for the mix ratios and what hardener the material uses.

My materials look like a second grader owns them but it has saved me from making a mistake more than once

same here^^^^ it can end up costing a lot of money not being organized.
Jay D.

NFT5 wrote:First, call the manufacturer and talk to the tech guys. Explain what has happened and ask their advice.

They may have a solution that will set the epoxy or it may be ok after a longer period or, worst case, you'll have to strip it off and start again.

You will get much better advice there than here since they are the ones who know the chemical composition of their products.

Once the solution is worked out I'd then be marching down to the local distributor and asking for free replacement product.

Three very cold days later, the epoxy seems to have hardened significantly. It retained it's gloss in that area, but I can no longer knick it with a finger nail. I have not tried rubbing a rag of thinner of it yet, which I imagine would be the ultimate test.

I have an email into the techs at Matrix, who are looking into the issue. We will see what they say, but I'm hopeful for some level of compatibility.

PainterDave wrote:strip it off, period. 5 gallons of lacquer thinner. start over.

yes your jobber may have sold you wrong hardener but they did not pour it into your paint.
learn to read tech sheets and double check products. 100% your fault the minute you mixed.

don't mean to sound harsh buddy but that's the way it is.

Does sound harsh, but I appreciate the perspective. I make it very clear when I go in to purchase the paint that I'm new to this, and make sure to ask them to select the product(s) I need.

As I said, you would hope customer service still exists, otherwise I could just order the material online. Instead I opted to go to a small local paint store in an effort to support the local industry. I respectfully disagree that it was 100% my fault, but recognize that I should have double checked everything.

I do read and understand the tech sheets, but when I've been sold the same stuff twice in a row, then go back for a third, you assume to receive the same product. But you know what they say about assumptions...

OldFatBald wrote:I keep a binder for all my tech sheets, then I write notes and use a yellow highlighter on mix ratios, pot life etc.

I also use a sharpie on the cans for the mix ratios and what hardener the material uses.

My materials look like a second grader owns them but it has saved me from making a mistake more than once

Sounds like a good system. I'm only working on the one car and buy the paint as I go, but I'll keep this in mind as more material is required in the future.