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PostPosted: Thu May 03, 2018 7:03 pm 
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Location: Seattle
Last month the Seattle Luthiers hosted John Greven a luthier in Portland. He described his pore fill method so I decided to try his recommended product. The epoxy he uses is System 3 SilverTip Epoxy with the fast hardener. He liked it because it was clear, it goes on easily is made to work on bare wood and wets the wood well. This is mostly a boat building epoxy. The other item he recommended was getting a box of blank credit cards to use as a scraper.
White Blank PVC Plastic Cards. I got 100 for less than $13 at amazon https://www.amazon.com/gp/product/B007M413BC.

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I applied a little at a time and used the card to apply and then squeegee most of it off. With the fast hardener I will sand most of it off this afternoon and reapply. I always use the first application of epoxy to find areas that need more prep because it shows up flaws just like a finish.
I am surprised that I am really liking how the Osage Orange looks. Also I am told that it darkens with age.

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Day 2

The epoxy seems fully cured in about five hours. So you can apply multiple coats in a day. The instructions say you have a 20 minute working time with the fast hardener which is plenty for me.

With this epoxy I wanted to try a new process for me where I come out of the pore fill with completely level surfaces and any required drop fills dealt with. I have gotten late into the finish process on guitars and have sanded through the finish, pore fill and\or the seal coat to wood when leveling the final finish. I am trying to avoid that.

So far the system 3 silverTip is easy to work with, it is clear not as thick as zpoxy, it does not seem to foam and I can leave on a very thin wetted coat.

This morning I leveled the finish with many sand throughs, checked for low areas. found a few places to drop fill and applied a second coat of epoxy.

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About five hours later I used a sharp scraper and a razor blade to level the cured second coat. I found a couple of missed drop fills, which I fixed with gluboost this fit and finish CA and applied what I hope is my final coat of epoxy. I plan to repeat the above until I have a perfect coat as there is no harm at this point in the process of sanding through.

After I leveled th epoxy
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with a fresh coat.
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Day 3

Just to close this off using a utility blade and a scraper I scraped most of the epoxy off. I was close but still had a low spot in one of the sides, and there were a couple of places I sanded down on the back as I saw some scratches through the finish.

In any case I put one more very thin layer of epoxy down (I spread an amount about the size of a quarter across the entire back and use one of the plastic cards to scrap most of that off.)

About five hours later, I scraped a couple ridges and drips toward the edges off with a utility blade (it just peels off in a very even ribbon).

After I had it level to my eyes I used a 800P Wet and Dry paper with mineral spirits as a lubricant. Here were the results after wet sanding

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I put on 3 or 4 wipes of diluted Seal Coat (really 1 lb shellac) and called the pore fill on the body done.

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To close I could of done this in a long day (2 or 3 applications) if I had properly prepared the body for finish. I have a hard time seeing all the flaws even with a naptha wipe. They do show up after wet sanding the epoxy though.

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PostPosted: Thu May 03, 2018 8:36 pm 
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Joined: Thu May 24, 2012 8:03 am
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Location: Chestertown Maryland
beautiful set of OO. What's the top?

Ed


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PostPosted: Thu May 03, 2018 8:43 pm 
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Location: Seattle
ruby@magpage.com wrote:
beautiful set of OO. What's the top?

Ed


Thanks, the top is Western Red Cedar

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PostPosted: Thu May 03, 2018 8:58 pm 
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Location: Chestertown Maryland
I have a nice piece of 65 year old redwood - now that you mention it - it would make a fine top for an OO guitar.

Here are 2 shots - one right as this 00 guitar was finished, and one a year later. It has not darkened much from the second shot now at 3 years. The heel cap is boxwood and it did not change color much at all.


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PostPosted: Thu May 03, 2018 9:08 pm 
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Location: Seattle
ruby@magpage.com wrote:
I have a nice piece of 65 year old redwood - now that you mention it - it would make a fine top for an OO guitar.

Here are 2 shots - one right as this 00 guitar was finished, and one a year later. It has not darkened much from the second shot now at 3 years. The heel cap is boxwood and it did not change color much at all.

Thanks for showing this, that back looks a lot like mine. It is interesting to see how it aged over 3 years.

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PostPosted: Sun May 06, 2018 12:38 am 
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Excellent post, John! So, compared to your usual method, what are your thoughts on the system 3 as a fill? Are you going to use it in the future?

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PostPosted: Sun May 06, 2018 8:55 am 
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Location: Chestertown Maryland
I have always wondered about leaving a coat of epoxy on the surface and how it affects sound - seems like it is a fairly heavy material and that it would be better to sand back to raw wood. Any thoughts? Guitar is looking great by the way.

Ed


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PostPosted: Sun May 06, 2018 11:33 am 
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Location: Seattle
ColestineGuitar wrote:
Excellent post, John! So, compared to your usual method, what are your thoughts on the system 3 as a fill? Are you going to use it in the future?

Thanks, I will try this epoxy again on a different wood with deeper pores. So far I like how easy it is to work with. I have used zpoxy quite a bit. This differers in that it does not have the amber tint also it has a lower viscosity making easier to push into the pores and easier to squeegee off leaving only a very thin even coat.

ruby@magpage.com wrote:
I have always wondered about leaving a coat of epoxy on the surface and how it affects sound - seems like it is a fairly heavy material and that it would be better to sand back to raw wood. Any thoughts? Guitar is looking great by the way.

Ed

Thanks Ed,
I only use it on the back. I am not sure how much the epoxy weighs relative to nitrocellulose or even shellac. I leave such a thin layer I am sure relative to the mass of the wood itself it is hardly worth thinking about. In any case I do a spectrum analysis of the guitar at various stages of the build. I design for an active back, so far I have not seen negative effects from the coat of epoxy. Extra mass would show up as lower resonance frequency and lowering of response. I see almost no difference between the response before and after the application of the pore fill.

My problem with sanding back to bare wood is I almost always open new pores, as sometimes the new pores are just below the surface. I might get by with scraping to bare wood, but in all honesty with both zpoxy and so far silvertip, I like the look it gives to the wood.

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PostPosted: Sun May 06, 2018 8:50 pm 
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Very nice post John. I'm curious if you've used Aquacoat, and your opinion of the System 3 vs. Aquacoat. I'm thinking of trying system 3 instead of Aquacoat. Is there much out gassing or odor with System 3?


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PostPosted: Mon May 07, 2018 1:19 am 
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Location: Seattle
Diane, I have used aquacoat. It is a lot easier to apply and sand off. I have yet to be happy with it though as I never seem to get rid of the pores. System 3 is a two part epoxy that chemically cures rather than off gasses. There is not much smell. I mix 10-20 grams at a time. It is epoxy so there is some volatiles.

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