How to prep bodies for painting?

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repoman
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How to prep bodies for painting?

Post by repoman » Wed May 25, 2022 7:58 am

Over the years I've spent quite a lot of time and money on products for painting hobby guitars. I have never, ever successfully prepared a body for paint however.

I've spent a stupid amount of money on grain filler products and have never gotten any of them to work as intended.
I was wondering if people could help shed light on what I am doing wrong in preparing the body for the base coat, color and clear.


My understanding of prepping is that the body should be thoroughly sanded to 240 grit, after which 2 coats of sanding sealer are applied to the body. A grain filling product is applied, let to dry, then the body is level sanded again. At this point the body should be closer to being ready, if it isn't another 2-3 coats of grain filler+sealer level sanding proceedures should take place. This should be enough to have the surface level for painting.

Products I've used and my observations of the results:

Aqua-Coat: this stuff applied sort of strange, it doesn't like to stick to the surface so getting it into pores/grain is very difficult if it does so at all. It also is heavily constituted of water and when dry the build is incredibly small per application.

Solarez: this is a UV cure epoxy. It takes very strong UV light to cure, fine if you have a lot of sun, I live in New England where sun is rare so it's a bit difficult to work with, UV lights take forever to cure it. Grain filling is VERY good and this stuff legit works. The problem I have with epoxy grain fillers is that the resin dries much harder and is far more durable than the underlying wood, this easily leads to areas of too much wood being sanded away while lumps of resin remain. It also sands poorly, clogs paper very fast and takes a long time to sand. This always winds up with me spot sanding troublesome areas which then leads to uneven sanding.

Z-Poxy: same story as Solarez, it grain fills excellently but presents a lot of trouble in sanding.

Stewmac/Timbermate: this stuff applies easily, is water soluable so clean up is fast, it sands excellently. However it seems to not provide any grain filling at all when paint comes into contact with it.

Behlens oil based grain filler: applies like Timbermate, doesn't really seem to fill grain much at all, however, if you do manage to get it into some areas that need filling, it does not sink and disappear the way Timbermate/Stewmac filler does. Another downside is that this stuff seems to not dry at all, I had a little bit in a cup for 9-10 days and it was still not dry.

Some finishing gore NSFW:

Here are two Coronet junky projects I'm painting trying to learn this, these two guitars have a guide coat of Duplicolor lacquer

Image

This headstock has two different attempts to get it to fill. It's AfMahog.
First attempt was:

2 coats Deft sanding sealer.
1 coat Behlens grain filler squeegeed in with a rubber spreader, then burlap rub.
Sanded flush.
1 more coat sanding sealer.
1 coat Behlens grain filler repeat.

I applied a guide coat and saw zero fill, sanded that as flush as I could then applied Timbermate in the same manner as the Behlens but did not use burlap rub.
Sanded flush, applied sealer. Sanded flush, applied 2nd coat of Timbermate, sanded flush. This is the guided coat as it sits now, basically zero grain fill.

Image

Same as above. Multiple attempts, this has been attempted to fill and level many times.

Image

This only has Timbermate, 4 different applications. I thought maybe the Behlens and Timbermate were interacting weirdly and the paint was pulling away from the grain areas from some funky surface tension thing so I just did this one with only Timbermate.

Image


Am I doing something fundamentally wrong? Should I just be spraying like 4-5 coats of sealer, level sanding that and then painting? It seems like that would be a million times faster and straight up better for surface finish at this point. Are grain fillers snake oil?

I did paint a guitar where I had spent much less time in making sure the sanding was done well, I painted it with straight up Tamco catalyzed urethane with no sealer and that came out very well, it covered up ever imperfection within 2 coats (3 coats of that stuff seemed to be equivalent to about 40 coats of lacquer). I do not have the facility to be spraying that stuff though and have to work with lacquer.

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Re: How to prep bodies for painting?

Post by PixMix » Wed May 25, 2022 8:41 am

I don't think spraying more sealer would do the trick here. Looks like the grain filler might have not been applied properly, as in it didn't fill the open grain of the wood.
I would try on some scrap pieces the following: get a small flexible plastic card (gift card, or similar), work in small sections and try to get a perfectly flat surface. You're trying to push the filler into the grain. Don't do the burlap, sand with 400 grit paper when filler is dry. Use a small plastic or pink eraser as a sanding block, sand flat without applying too much pressure. Repeat grain filler step one more time if the surface is not perfectly flat. Once you get a flat surface, by this I mean no open grain is visible, go on to your next step.

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Re: How to prep bodies for painting?

Post by repoman » Wed May 25, 2022 8:53 am

What grain filling product do you use?

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Re: How to prep bodies for painting?

Post by wdc1195801996 » Wed May 25, 2022 9:31 am

Can propylene be used?

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Re: How to prep bodies for painting?

Post by repoman » Wed May 25, 2022 9:42 am

wdc1195801996 wrote:
Wed May 25, 2022 9:31 am
Can propylene be used?
Whats that?

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Re: How to prep bodies for painting?

Post by repoman » Wed May 25, 2022 9:47 am

repoman wrote:
Wed May 25, 2022 9:42 am
wdc1195801996 wrote:
Wed May 25, 2022 9:31 am
Can propylene be used?
Whats that?

Also, I have a lot of trouble "reading" the surface of the guitar, when I hold it at an angle to a source of light to see how the sheen lays, it's always seems like the surface is level, but then when I put on the guide coat, it reveals a very horrible prep job. I guess that is the point of a guide coat but then you have to deal with the added potential problem of the guide coat not working with the next application of grain fill.

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Re: How to prep bodies for painting?

Post by fleezinator » Wed May 25, 2022 12:32 pm

I've used Aqua Coat and a Timbermate like product called Goodfilla. Both shrunk after a months time. The top of the surface is smooth and mirror like but the foundation layer reveals the flaws.

Image

Since the I've tried UV Solarez , Varathane Ultimate and Crystalac Brite Tone as grain fillers. I think Solarez and Brite Tone work well. Crystalac Brite Tone is really high solids and with a 2-3 coats serves as a great base, is self leveling, and sands easy.

For my JM build I filled with Varathane and then used Createx Autoborne Silver Sealer mixed with Createx Wicked black to make a charcoal color before moving on to Createx Candy 20 in Blood Red to make a TVL like Oxblood. Then I clear coated with more Varathane. I've played it shorter than the tele I finished with Brite Tone and it doesn't have the same durability as Brite Tone.

For future builds, I'm sticking with Brite Tone as filler/sealer/top coat & Createx for color/metallic/pearls/candy.

Image

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Re: How to prep bodies for painting?

Post by Steadyriot. » Wed May 25, 2022 12:34 pm

I’d also say you’re applying your filler wrong, or are using the wrong filler.
Over here in mainland Europe it’s pretty hard to come by grainfiller. One that is available is from the German brand Clou, which has worked great for me in the past. Rub it in, scrape off excess with an old credit card, sand smooth (wouldn’t go lower than 240 but I like 400) and you’re ready to paint. I’ve used plaster of Paris before too with great results. Granted I haven’t tried mahogany yet, but swamp ash can get pretty grainy too.
Note: these ‘traditional’ fillers will shrink a little over time, but that’s part of the game. I’m not using nitro for its durability either.

The way I do it:
Wet the body and sand, repeat until it doesn’t get “hairy” anymore. Apply grain filler, nice coat of primer, sand if it doesn’t sit nice and flat, if the grain isn’t perfectly filled, add some more to problematic spots, add another layer of primer if needed. Sand if it’s not smooth yet, 400 grit. Then it’s time for color, don’t skimp on that. 2 cans should do it. Add a lot (again, 2 cans) of clear et voila! Some wetsanding and polishing and you’re done.
Image

Also gonna need some pic’s of those Coronet’s in full!
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Re: How to prep bodies for painting?

Post by Lost In Autumn » Thu May 26, 2022 2:00 am

I would apply more grain filler until the grain is filled. I'm using Crystalac Grain Filler and Brite Tone Instrument Finish- I keep applying the filler until I have a smooth surface. Then, I'll spray a shellac based primer, sand, spray my color coats and finally, clear coat before level sanding from 600-15000 grit, buffing, polishing and waxing. the best advice I can give you is that you have to be patient. It doesn't hurt to apply more coats of filler or finish; you've already experienced the results of not applying enough.

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Re: How to prep bodies for painting?

Post by Jazz Master » Thu May 26, 2022 2:41 am

I've been using Timbermate as grain filler on wood here in the USA, comes in different colors if you are using an opaque paint
After primer sealer ~~~
You have to apply it with a bondo spreader = credit card in both directions = with & against the grain & leave a layer on there until dry & then sand it smooth, If more is required do that step again, It sands very easily BTW
When I worked at an auto body shop they used body putty after the primer sealer to fill scratches left by the previous sand paper, it was in effect thick red primer & also sanded very easily & was applied with a spreader & leveled the surface, being it was a contrasting color you could see it easily

HOPE THIS HELPS

I have a guitar here I have done a repair on that needs more primer & sanding to make the repair VANISH
It has not had the Timbermate used on it YET BTW

2007 Parker Fly Deluxe with a Nasty Scratch = $3000 Guitar
Image
Image
Image
Image

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Re: How to prep bodies for painting?

Post by repoman » Thu May 26, 2022 6:23 am

Thanks for all the help!
I will check out these Crystalac Brite Tone products.
As far as application, I am using one of those urethane spreaders:

Image

Do you guys spread this in, let dry and if you need more coats apply something like a sealer, varnish or shellac over it to seal it to prevent it from pulling out on the next application?

I thin it a little bit with water.

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Re: How to prep bodies for painting?

Post by repoman » Thu May 26, 2022 6:32 am

fleezinator wrote:
Wed May 25, 2022 12:32 pm
I've used Aqua Coat and a Timbermate like product called Goodfilla. Both shrunk after a months time. The top of the surface is smooth and mirror like but the foundation layer reveals the flaws.

Image

Since the I've tried UV Solarez , Varathane Ultimate and Crystalac Brite Tone as grain fillers. I think Solarez and Brite Tone work well. Crystalac Brite Tone is really high solids and with a 2-3 coats serves as a great base, is self leveling, and sands easy.

For my JM build I filled with Varathane and then used Createx Autoborne Silver Sealer mixed with Createx Wicked black to make a charcoal color before moving on to Createx Candy 20 in Blood Red to make a TVL like Oxblood. Then I clear coated with more Varathane. I've played it shorter than the tele I finished with Brite Tone and it doesn't have the same durability as Brite Tone.

For future builds, I'm sticking with Brite Tone as filler/sealer/top coat & Createx for color/metallic/pearls/candy.

Image
That looks awesome.
Are you using the Varathane oil based or waterbased products?
Do you spray water based products outside? I've tried using waterbased stuff (General finishes precat lacquer) in the past spraying outside and had really horrible results (mega fisheyes and it would take ages to dry even in <50% humidity)

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Re: How to prep bodies for painting?

Post by fleezinator » Thu May 26, 2022 9:16 am

repoman wrote:
Thu May 26, 2022 6:32 am
That looks awesome.
Are you using the Varathane oil based or waterbased products?
Do you spray water based products outside? I've tried using waterbased stuff (General finishes precat lacquer) in the past spraying outside and had really horrible results (mega fisheyes and it would take ages to dry even in <50% humidity)
Thanks! I used water based Varathane Ultimate for my JM. It was nice that it was cheaper and easily accessible in my area than Brite Tone, but performance wise, the Brite Tone is the harder finish.

The fisheyes usually is a result of some kind of contamination or incompatibility. I initially tried to mix Mixol tints in with Varathane with bad results. My current Createx + Brite Tone work flow doesn't have this:
Image

Spraying wise, I use a Rockler HVLP : https://www.rockler.com/rockler-hvlp-fi ... prayer-bdl
The trick is to use a Preval jar to use smaller quantities of paint: Image

I tried spraying in the garage with a shoddy cardboard booth using solvent rattle cans. Even with a respirator, it was nasty smell that lingered. So I took the booth outside and got terrible results due to gusts of wind.

Before (rattle cans + cardboard booth) & After (stripped the first attempt, started anew with HVLP & spray booth)
Image
Image

I ended up scrapping that attempt and built a janky spray booth using a popup tent, plastic liners & a bunch of clips & tape. Two fans, one for intake, another for exhaust. At this time I also switched over to all water based, so no risk of explosions in the booth. JankyAF but works a treat!

Image
Image
Image
Image

In my case, the Houston area weather is constantly humid and thankfully water based finishes deal with that fine it seems. Overall, I've learned that the biggest factors to success is having a sprayer for even & consistent coats as well as a controlled environment that removes debris & wind out of the equation.

My 3 results with the setup:

Image
Image
Image

More context here:
https://imgur.com/a/pha991R
https://imgur.com/a/pShpqs2
https://www.tdpri.com/threads/a-newbs-f ... l.1030073/

Hope that helps!

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Re: How to prep bodies for painting?

Post by Lost In Autumn » Thu May 26, 2022 5:47 pm

repoman wrote:
Thu May 26, 2022 6:23 am
Thanks for all the help!
I will check out these Crystalac Brite Tone products.
As far as application, I am using one of those urethane spreaders:

Image

Do you guys spread this in, let dry and if you need more coats apply something like a sealer, varnish or shellac over it to seal it to prevent it from pulling out on the next application?

I thin it a little bit with water.
Don’t thin it. It wants to go on thick.

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