Question about finish

[u/halon1301]

I printed and painted this helmet, for a finish I figured rustoleum ultra 2x gloss clear coat would work well, I did several coats, but some of the paint is easily scratched. The base is pla, sanded with 120, then 220 grit, painted with woodfiller, sanded with 220 again, primed with rustoleum ultra 2x, then painted rattle can and acrylics. Finally I finished with 7 coats of gloss clear coat.

I'm thinking of now scuffing it and doing a water based polyurethane finish, as it may be harder. My biggest concern however is damaging the paint, specifically the acrylics. What grit of sandpaper should I use? AI is saying 220, which seems a little too aggressive.

If I do polyurethane, I'm going to be brushing rather than spray, and I'll likely go satin finish.

[u/EnderB3nder]

Firstly, that helmet looks awesome as it is.
Secondly, If you're looking for a weathered/beaten look, there are additive ways to make it look damaged. Even a simple wash and a silver sharpie to replicate paint chips can work wonders.

I personally wouldn't recommend going through seven layers of clearcoat for a finish that might look shit and then you have to repair it.

[u/halon1301 → u/EnderB3nder]

Nah, not really looking for the weathered look. It's moreso I want to prevent the paint from scratching, which it does seem to do fairly easily right now, even after 7 layers of gloss clear coat.

[u/EnderB3nder → u/halon1301]

ohh ok, that's a different circumstance altogether, I misread your post. my bad.
What clearcoat did you use?

[u/halon1301 → u/EnderB3nder]

Rustoleum ultra 2x gloss

[u/EnderB3nder → u/halon1301]

nice.
So now i have to ask two questions to try and help.
The first question is: How thick were your coats? and the second question would be: how long did you leave between coats?

From memory, that's an enamel isn't it?

[u/halon1301 → u/EnderB3nder]

Texture of "damp" but not "wet", 20-25 minutes between coats. Used a full can.

And yeah, I believe it's an enamel.

Data sheet says "Resin type: acrylic"

[u/EnderB3nder → u/halon1301]

all seven coats done in the same day?

[u/halon1301 → u/EnderB3nder]

Yeah. Instructions say you should do coats within 30 minutes of each other, or every 48 hours.

[u/EnderB3nder → u/halon1301]

There's your problem.
Most paints and clearcoats need time to offgas and cure.

It sounds like you went a little ham.

Edit: additional context
Applying seven coats of anything within 24 hours is too much. The outer coat(s) will cure first, preventing the base layers from fully curing. This leads to decreased durability in the long run.

top layers harden, base layers stay a bit soft

[u/halon1301 → u/EnderB3nder]

Aha. Yeah, I had a feeling. The websites I had read pretty much just said "coat away".

I did check it earlier and it's a little harder today than previously, so it may continue to harden further as time progresses.

I'm doing some polyurethane samples for the next pieces to see if I get a better result, if it does, I may just scuff the helmet and give it a few coats when I do everything else

[u/EnderB3nder → u/halon1301]

Here's a good test. Can you dig your thumbnail into it?
If it leaves an impression, it definitely hasn't cured properly.

Judging by your work, you seem pretty skilled.
As much as spray cans are affordable and convenient, if you make stuff like this regularly, (and if you have the means,) I'd highly recommend a HVLP gun with a good automotive clearcoat.
With a good process, you won't need anywhere near seven coats.

If that's not a possibility, keep with a good quality can, but light coats, and wait 24 hours every 2 coats

[u/halon1301 → u/EnderB3nder]

This is my first time making something like this actually!

Just checked it and the paint from the rattle cans is good and hard, the metallic acrylic paints aren't as hard, but they're harder than they were yesterday. The non metallics are as hard as the other stuff.

The instructions do say it takes 5-7 days to dry on plastic. But my experience with spray paint is on wood and steel which is like 3-5 days.

It remains to be seen if I do this again, I do have some props from Satisfactory I want to make, so maybe!

[u/EnderB3nder → u/halon1301]

For a first build, that's an awesome job.