Acrylic Rattle Can Finish

[McCreed]

Really not a problem with that product. If you follow the instructions it will smooth out as it dries and requires no final step.

Yep. I've become a convert to satin poly on all my necks now. I also use Cabot's but I spray it with a gun or airbrush, not rattle cans, though it's a very similar formulation.

As Sonic said, if you get your last coat to lay on nicely (and you don't have a GD bug land in your wet finish coat - don't ask me how I know!) all you need to do is let it dry.

I'm still big fan of gloss on the body though.

[kman42]

Do you guys have a problem with soft finish when using poly out of rattle cans? 3 months after finishing my guitar with satin Cabot's exterior poly (3x triple coats) I can still dent it with my fingernail if I press hard. It's not woefully soft, just softer than some of my furniture finished with a poly varnish (brushed). Is it just because the finish is too thin, or is spray poly a bit softer?

[Simon Barden]

It’s still a relatively thin coat, and hard to say anything without seeing it in the flesh.

Did it go on over a stain or something like Dingotone? If the latter, then the finishes may not be 100% compatible and one is stopping the other from going fully hard.

But it may just be that the body wood is soft and a thin layer of poly can only provide so much support and strengthening. If you want a thin finish, then it’s not going to be as hard-wearing as a thicker finish would give.

I’ve got no experience with that product, so can’t suggest anything more definite.

[Sonic Mountain]

Finish should be pretty much rock hard. Are you sure it's the finish and not the wood itself as Simon suggested?

Some things that may be contributing to what you describe.

1. Application too thick. You need to make sure there is sufficient drying time between coats. What can happen if you build up too thick an application is that the top of it will skin off to a point where the bottom layers can't fully out gas. This can sometimes be fixed by sanding back the top coat and seeing if that allows the bottom layers to dry out

2. Applied during conditions that were too hot or cold. Too hot can result in the above as the top layer flashes off too quickly. Too cold can mean it will just not cure properly at all.

3. As Simon mentioned, incompatible products can be problematic, but that said, I am yet to find anything that really reacts badly to poly - as long as the initial product is completely dry. I've sprayed it over various stains and even hobby acrylic paint with no problems at all. I would suspect that enamel would be a problem, but I haven't tried that.

4. You may have got unlucky with the batch of Poly, unlikely, but can happen.

If you put you nose up against the finish, can you still smell the poly? if so I would put a fan on it for a while and see if that helps. After 3 months if it's not hard you might be looking at stripping it back and having another go.

[kman42]

This was sprayed over a spirit-based stain - https://www.bunnings.com.au/feast-wa...stain_p1569964
It was sprayed in fairly mild weather, so I don't think its a temperature problem.
I didn't feel that the coats were overly thick, but I have no reference point. I'm hoping its just that I don't have enough coats. I'm spraying another guitar with the same product, and will use more coats, so I'll have a comparison.

Sonic Mountain - when you say 'Application too Thick', that sounds like a separate issue to sufficient drying time. I believe I'm leaving it long enough to dry (3x light coats, 5 minutes apart, then leave it 3-5 days (weather dependent) before spraying the next triple-coat). In regards to 'application too thick', are you saying that if I sprayed a very heavy single coat, it will never cure fully?

[Sonic Mountain]

Yeah, a very heavy coat can cause the problems you describe. The same thing if you don't wait long enough between the light coats, but what you have described should be fine, that's exactly what I do. I've used it over those Feast Watson stains many times with no problems so that's not it either.

It's a bit strange, it seems like you've done the right thing. Does it still smell like poly if you put your nose up to the finish?

I'd probably try putting it out in the sun for a while and blowing a fan on it to see if that helps.

[kman42]

No, it doesn't smell. Maybe I'm expecting too much of the poly - I have to press pretty hard with my finger nail to make an indent, and it sounds like the coating may be too thin.

[Rodc]

I retract my statement about having no luck with acrylic paints. Sprayed 2 now and followed the directions this time..
Since SM has mentioned Cabots exterior that's all I use now on a finish. I love it, it's so forgiving. I've used up to 3 cans on a body and neck. Bit over the top but the finish is great. Bit slow going now it is winter, I'm leaving it for 24 hours before I re-coat. Light sand in between with 000 synthetic steel wool..