Acrylic Clear Coat

[Neohet]

Hi guys,

I am currently 'finishing'? my first project - an old Strat 'style' guitar that my girlfriend bought for £10 years ago and then abandoned in the attic.

It apeared someone had tried refurbishing it previously, probably hand painting it! and the gig bag it was in had become one with the body

Anyway, I managed to remove the gig bag, stripped off the naff paint job, sanded the wood smooth, sealed with epoxy resin, sanded smooth again, sprayed with primer and then 4 coats of gorgeous purple metalic (from rattle cans admittedly, but I was very happy with the results at this point).

The only thing was that although the paint was supposedly quick drying (it was dry to the touch within 10 minutes) it then seamed to take an age to harden, and I didn't want to start with the clear coats incase I built up too thick a coating of soft paint that never hardens.

After 3 days, if I pressed firmly I could leave finger prints which dissapearded when pollished with a soft cloth. After 5 days it no-longer left finger prints but I could leave marks with a finger nail.

By now I was itching to get the job finished, as I hope to give the guitar back to my girlfriend for X-mas, looking like new.

So I then moved on to the clear coat. The only clear I could find in rattle cans (I don't have a spray rig, but I'm hoping to get one for my next project - a complete build from scratch) was Clear Acrylic. I sprayed a couple of coats then left it to dry, not wanting to build up too many soft coats again.

I then found this site and read a lot of the great tutorials and tips you give in your posts.

It seams that 'Laquer' or poly-urathane are the prefured clear coats, (I always thought Acrylic was a laquer BTW) and I have read that Acrylic is not that durable?

Sorry for the long post but my questions are these:

1, Have I made a bad move by using Acrylic? Will it never harden to the same sort of finish as you get on a commercial guitar?

2, What is the reason behind sanding back between coats? is it just to correct any imperfections such as dust or orange peel surface? The reason I ask is that I have now sprayed 4 coats of clear and at this point it's sugested I should sand back before spraying another 5 or so then sanding again before a final coat then polishing, but at this stage I'm quite happy with the smoothness of the finish (its almost like glass, just a little soft and could do with being thicker/deeper). Is there any need to sand or can I carry on building up the thickness?

3, If I have to sand back, am I best to wait until it has realy hardened each time? (if it ever does?)

4, I know that when re-spraying a car/body panels, many spray-shops bake the paint job in an oven. I have access to an industrial drying oven at work. Has anyone used or would you recommend using a drying oven? Would this harden clear acrylic as hard as a commercial finish? or would it cause cracking or other detrimental effects? If so, at what sort of temperature?

Finally, I read in one tutorial that when applying clear coats you should spray a coat then wait around 20 minutes or so then add the next coat while the first is still tacky? and that you shouldn't leave it too long between coats. Due to only having short periods of time free I've done a couple of coats 30 minutes apart then left it untill the next day (24s hour or so) before doing the next couple of coats. Is this going to cause any problems?

Sorry again for the length of this post, Hope someone manages to plough through it and can help.

Regards,

Matt.

[GuitarGuy]

4, I know that when re-spraying a car/body panels, many spray-shops bake the paint job in an oven. I have access to an industrial drying oven at work. Has anyone used or would you recommend using a drying oven? Would this harden clear acrylic as hard as a commercial finish? or would it cause cracking or other detrimental effects? If so, at what sort of temperature?

Baking is an accelerator for the finish. The warmer it is the faster it dries. The hardness of a factory finish comes from the fact the it is a 2-part paint. Much like an epoxy it has a resin and hardner.

From a spray can acrylic the hardness is based on how dry it is so in that respect heat may help. But I would avoid it if possible. Not a good idea when using heat and wood together.

[Neohet]

Thanks for that GuitarGuy, I thought as much, guess I'll just have to be patient

I'd still like to know if I should sand back at this point or carry on building up the thickness, and if I should wait for the current coats to harden fully, i.e weeks rather than days?

Regards,

Matt.

[tasty]

If you must use rattle cans (like I do) I would suggest the DEFT lacquer as one of the best. Just be sure to do a complete compatibility test on a scrap piece of wood to see if your primer, color coat, and clear lacquer all work together. I had great results with the DEFT and it is readily able to be purchased everwhere (even WAL-MART). Hopefully your clear will be okay already but in the future you may want to check out DEFT lacquer. The only real drawback is that you have to wait like 30-60 days (or more) until the stuff gets really hard.

Hope this helps.

[rhoads56]

I use a heat box for my guitars, which gets up around 45-50 deg C. You do the conversion to F.

Acrylic IS lacquer, just a different type.

Eventually it will dry out and harden, but it might take a while.

[Mickguard]

I've done two guitars with acrylic rattle cans (automotive stuff). I'm really pleased with the results. It takes a good month or so for it to dry (took less in the summer, but I let it sit a whole month anyway). I just put it in the closet and forgot about it during that time.

Is acrylic as good? Maybe not. But it's accessible and looks close enough to the the real thing.

I didn't worry too much about the color coat. It's job is to provide color, not durability. And once I start spraying the color, I tend to keep my hands off the guitar --either I screw a plank into the neck pocket or in the case of my current project, I rigged up a hanging system using dowels through a couple of tuning holes. I won't touch the guitar again until after the clear coat has cured for a couple of weeks at least. And even then it's just to pet the guitar for a couple of seconds and put it back in the closet.

As for the sanding back...I've read people who say they do, people who say they don't.

I didnt. Partly because it doesn't make any sense --as long as you don't have any massive ugly drips, that is. The only layer you need to have perfectly smooth is the final layer. Which is the one you sand AFTER the clear coat has fully cured. And then you polish that, and you get that magical feeling when the guitar starts to shine.

So patience is the game. In the meantime, you can get started planning the next guitar.

Do a search for posts from Maiden69 --he's given lots of great finishing advice here, he helped me out a lot, and he's done some great work.

[marksound]

And even then it's just to pet the guitar for a couple of seconds and put it back in the closet.

[Mickguard]

And even then it's just to pet the guitar for a couple of seconds and put it back in the closet.

←

You haven't actually built a guitar yet, otherwise you'd understand...

[rhoads56]

pro tip: with acrylic, the outer skin of the lacquer dries up, leaving a semi soft core. Break the surface by rubbing it back with 400-600 grit. This will allow the lacquer to "breathe" and dry out quicker. Might speed things up by about 30% but thats just a guess.

[Mickguard]

Well, in my case, it's taken me so long to build this thing, what's an extra couple of weeks?

Got plenty to do around here while I'm waiting!

[Mattia]

Re: heat, I recall a post not too long ago from someone who baked a whole body in his oven, and got cracks all over.

40-50 degrees C (what Perry said) is fine, but don't go crazy!high on this. You're not trying to dry out the wood completely.

[Mickguard]

I built a paint booth --it's tall enough to hang the guitar, and its surrounded in plastic to keep the dust out. (I have a well ventilated garage)

Once I'm finished spraying, I'm thinking about insulating it from the outside (got plenty of material lying around) and putting a lamp in there, say, a 60-watt bulb to warm things up a bit --what do you think about that idea?

I'll only need to keep it warm for a few days, until the worst of the fumes have dissipated, then I can move it indoors to a remote closet.