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I filled my first guitar yesterday using Z-poxy. I loved the ease of application but man is this stuf tuff.
I normally use 220 to level after filliing but it hardlly touched it without a lot of elbo grease.

The manufacturer recommendes 80 followed by 120 grit but this seams very agressive to me.

What has worked for those of you who have had some esperience with this stuff. I need a boost up the learning curve.

Cecil

Dont even think about 80 grit.I would go with at least 150, just take more time. It's best to level as carefully as possible when you apply it to reduce sanding.

Al

I've used a different brand of epoxy on my #2 which I'm sanding off at the moment. I got the back done last weekend and wasn't looking forward to the sides this weekend. Kiwicraig suggested I use a scraper. So that's what I did, scrape down until I almost hit wood (the shavings start to change color when your at the wood) and sand with 220 from there. Much, much faster.

Oh, and my epoxy took a few days to cure enough to sand, it's winter here though.PaulB38871.9509027778

Paul said it, just try a scraper, with a not too aggressive burr, then sand. When filling remember that you are just trying to fill the pores so a little goes a long way, the less you put on the less there is to sand off.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

Great advices here Al, Paul and Colin, i'm saving this for future reference, thanks!Serge Poirier38872.4225810185

Keep in mind the mahufacture make this product as a finishing resin for fiberglass construction, not as a pore filler. so the instruction will reflect its normal product market use i.e. The top coat on ,let say a fiberglass rc airplane. Wich will be may times thicker than what we put on a guitar to fill the pores.

I suggest you ose 150-220 depending on how much You left on the guitar. But as you get close to the wood you might want to go as high as 320.

I sand back just to the wood with 220-320 but I don't leave much of an access film on the guitar in the first place. If no more pore filling is needed to fill all pores, make up a batch of 40% alcohol 60% Zpoxy. this is very very thin, almost water thin. Then take a lint free cloth and wipe the guitar. This will level out your color all over, without adding any film thickness to speak of. do not sand this back. Let it cure 24 hrs min. When readdy to finish very lightly sand with 320 then apply two seal coats of your favorite sanding sealer. mine wax free shellac. Ths give a good bonding surface for your finish.MichaelP38872.6313194444

Cecil, I just finished using z-poxy fill for the first time and learned a few things...

In sanding back Z-Poxy, I'm with Paul and Colin and others in using a carefully-sharpened scraper. I quickly found out that the scraper should have a very smooth and even burr so you don't get any deep scratches!

For the back I chose to use my Bosch random-orbit sander (with a 220 grit disc, sander slowed down to medium RPM's) to smooth the epoxy fill, and followed that with hand sanding with a block. I know that others recommend finer grit papers, but I'll be using a nitro finish and 220 should leave a good surface for lacquer to adhere to.

On the sides and the back, I applied the epoxy as thin and evenly as possible, then sanded back to the wood each time using 220 grit paper. It took 3 coats to fill all the pores in the rosewood.

Michael, There's one part of the z-poxy finishing process I'm still not clear on...

When you lightly sand your final wiped-on coat of z-poxy, how do you sand it without going through the thin film anywhere? Do you apply only very light pressure to the sanding pad, only knocking off any small nibs that might be on the surface? Does much of the z-poxy surface remain 'shiney' before you apply the shellac?

Yes light pressure, 320 paper or even 400 if you wish. dull the surface evenly as best you can with out sandin into the wood. TThis is not much of a sanding, the objet her is not to sand back the film, but to create a good surface for the shellac to adhear to. The task is to create a ggod mechanical bond. If in very small areas you go through the zpoxy not to worry too much. the shellac will bring the color back. if you go through in quarter size or larger areas then lightly re-wipe those areas with 40% alcohol and 60% Zpoxy again, allow to cure over night and lightly sand that area.

Keep in mind that this final sanding is not a leveling process it is only to create a matt surface to the shellac sealer to adhear to.MichaelP38872.6303125

Many thanks to everyone for your most exececlent advice. This is the best prepaired surface I have ever seen.It should yeld a very good finish.
Just add this to the many things I have learned at the OLF University of the Guitar.

Cecil

I just wanted to add a little, hmmm explanation of how little to leave on. And only becase I think it isn't too clear how very little should be built up, I know I sure had no clue. And keep in mind I have only done this 3 times. the first one was so bad I had to learn real quick. Also I used system 3 which should not matter and added silica powder which may matter.. Anyway I the first time without silica, I spead it out and it was way way way to thick, it ran it settled it did everything wrong... It was very hard to scrape and sand level, but it sure did have some epoxy on it. The next time I added silica, which some use, some don't, but when I applied it, I used a credit card to smooth it into the pores and then with the card wiped off as much as I could. the surface was dampened, but there was no layer. the pores were filled due to the silica. My only point is to remove as much as possible from the surface while its wet. Leveling will be a breaze. the next time I am going to use Michaels thinned last coat as that sounds like the cats meow,,, what does that mean anyway..
Oh by the way, use a current credit card, it will get all messed up and save you money in the long run.
Mike

I use 320 on my RO sander to scuff the filler prior to finishing. The key is to apply it smooth so there aren't any ridges left to sand off. If you see any ridges, use a scraper to remove them in about 15 minutes after the filler has kicked.

Use a 3M yellow 4" or 5" plastic auto body bondo applicator to apply the Z-poxy on the sides and back. Then use a w-i-d-e window squeegie on the back to level the entire back in ONE swipe. Clean the applicators immediately with DA.

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tim...
http://www.mcknightguitars.com

Following a previous post, I have tried some test samples of Z-poxy on scraps of EIR and Cuban Mahogany to check for the colour change and was happy with the results. However, when it was curing, the smell reminded me of the self-levelling stuff that goes on concrete floors prior to putting down vinyl flooring, and also the cement used to lay ceramic floor tiles on wooden floors. I am wondering if there is some latex in the mix of Z-poxy, and if so what - if anything - this does to the sound of the guitar box.

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Dave White
De Faoite Stringed Instruments
". . . the one thing a machine just can't do is give you character and personalities and sometimes that comes with flaws, but it always comes with humanity" Monty Don talking about hand weaving, "Mastercrafts", Weaving, BBC March 2010

There is no latex in Zpoxy, and if you do it right there is so little left on the guitar I doubt it could have much of any affect on the sound. No more so than egg whites, past filler of pumice fill would have.MichaelP38873.3762962963

[QUOTE=ToddStock]

Tim - your suggestion to use a single pass on the back with a wide window squeegee and full width on sides with a Bondo applicator make sense from the viewpoint of time and effort, but I have a few questions:

- How do you keep the filler in the pores?
- Do you do this on every coat
- Are you using any silica, or straight resin?QUOTE]

- I apply the Z-poxy with the grain. I know this sounds counter intuitive but it works for me.

- Yep, every coat. One coat usually does it for me and I rarely need two except for Hickory. If I sand through then I just apply a wipe coat on the bare spot with a soft cotton T-shirt scrap.

- Nope, straight resin.

If I have a few pores that are a bit low, I don't worry about it because the first three coats of catalyzed lacquer will fill any low spots.

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tim...
http://www.mcknightguitars.com

I never have any problems on the backs, its the sides that are challenging to me.

I must admit however that I do put it on a little thicker than recommended, leave a little more on than some do and let it sit 48 hours before I sand back. I use an old credit card and use the cross grain method at a 45 degree angle. I then use a scraper and then go to 150 grit sandpaper and work my way up to 320. Once there I use the MichaelP thin coat to pop that color and grain back out and move to finish.

I think the photo above is representative of what I would run into as well, I call it overworking the resin. Trying to pull it down to much in the card scrapping process I think we end up pulling alot out of the grain pours partly due to variances in mixture and the drying process that really starts taking place pretty quick after you begin. If you notice on your card the color starts changing during the squeegying process. So, not meaning to make this long, but I go on heavier, since I am going to scrape, sand and thin coat again and have found my pours are filled after one coat.

Mike
White Oak, Texas