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Thread: Back removal

  1. #26

    Default Re: Back removal

    I always thought that these are the sort of things that, at least in part, begat "sunburst" (or black!) finishes.
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  2. #27
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    Default Re: Back removal

    Nobody sitting across the room at a jam can see all the flaws in my mandolins (nor do they care), so I just play them, and your secret is safe with us!

  3. #28

    Default Re: Back removal

    Thanks again for the advice.

    Is there some type of adhesive that does not darken the dust? Will varnish hold the dust in the oversized channel sections? Will the cherry dust darken like the solid wood does?

    Otherwise, I guess I'll try some wood putty (maybe) from the hardware store. Or not.

    I'm so conflicted here. Thanks for trying to help me sort this.

    Gary

  4. #29
    Registered User sunburst's Avatar
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    Default Re: Back removal

    Quote Originally Posted by GaryDavis View Post
    ...Is there some type of adhesive that does not darken the dust? Will varnish hold the dust in the oversized channel sections? Will the cherry dust darken like the solid wood does?
    It is the wetting of the dust that makes it darker, just like wetting the wood surface makes it darker (temporarily with water, more permanently with finish or glue because the "wet" look persists when the finish or glue dries) so no, there is no adhesive that will not darken the dust.
    I don't think varnish will hold the dust in place as well as glue, although it might work.
    Dust, used for filler, will probably darken like cherry wood does, but almost certainly at a different rate from the wood itself. I suspect that a good initial color match will gradually become less so as the colors darken at different rates.

    FWIW, I still don't recommend using wood dust and glue to fill the purfling channels, but here are some basic tips for using wood dust as a filler.
    As Pops said, dust will be darker than the source wood when mixed with glue or adhesive. Before I picked up this trick from Frank Ford I kept little containers of dust from various woods, from very light to very dark. I could mix them to get a good (but never great) color match. They only work well and look acceptable in very small fills, generally.
    If a fill is too light in color or shade we can darken it. If it is too dark, we're stuck with it or we remove it and try again.
    If I have to fill something I try for a decent color match but a lighter shade, and then I use drawing inks and dyes to work on the color, draw in grain lines and pores and that sort of thing.

    If I were to attempt to fill a purfling channel around a cherry back with any filler, I would not expect success in terms of a minimally visible result. Perhaps it is possible, but it is beyond my skill level, which is admittedly pretty good.

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  6. #30

    Default Re: Back removal

    OK John. Thanks for that.

    Sorry for beating a dead horse, but what would be recommended other than wood putty? Seems putty would be more problematic, from a color change perspective, than would cherry dust and an adhesive but what do I know?

    Any other advice and insight would be appreciated.

    Gary

  7. #31
    Registered User Charles E.'s Avatar
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    Default Re: Back removal

    You could try to make your purfling channels as even as possible and make a wood strip out of the same material as the back. Then inlay that into the channel.
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    Default Re: Back removal

    If you need thin strips of wood to inlay into the purfling gap, it's hard to get them in once they have glue on. I cut strips to fit cracks and insert them dry, then wick in hot hide glue. It is mixed thin enough to wick and securely holds. It also works great for small top and back cracks. That way you will have the same wood and it may still be a visible repair, but not as much as dust. As others have said play it, when you look at the spots that aren't perfect it will inspire and remind you to focus more on that area next time around.
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  10. #33
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    Default Re: Back removal

    It seems to me that filling the channel and re-installing violin style purfling would be an endless headache and would look like a patch job no matter how much effort you put into it.

    Instead, why not file the edge flush to the sides, and install binding and purfling like a guitar? Depending on the width you would need, you could use double or triple line purfling, or if you need something wider, perhaps the checkered or diagonal pattern purfling strip [part # PFMQ4 from LMI] that is easily available.

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  12. #34

    Default Re: Back removal

    I have filled the biggest gaps with wood slivers. The rest of the imperfections are too small for slivers (at least at my skill level).

    Going with traditional binding won't work because the purfling sits on the rims and I can't remove enough to get rid of the purfling. But maybe. And that only works on the back. The top is better than the back and no way can the edges here be modified and still look correct.

    I'm going to work on those channels with a little sandpaper to see if I can rid the channels of these errors. Some will sand out but others (most) won't.

    I really appreciate y'all that have stepped up and tried to help me out. I've still got a bit of finish work to do before I have my real luthier slot the nut and string it up. If it sounds like a mandolin, I'll keep at it and varnish the body. If it sounds like a cardboard box, onto the mantle it goes. Its been an incredible learning experience and I'll appreciate your help.

    Gary

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    Default Re: Back removal

    Plane shavings can be very thin and can be inserted into a fine crack dry. Just a thought if you want to try some of the smaller gaps.
    THE WORLD IS A BETTER PLACE JUST FOR YOUR SMILE!

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    Default Re: Back removal

    Quote Originally Posted by rcc56 View Post
    It seems to me that filling the channel and re-installing violin style purfling would be an endless headache and would look like a patch job no matter how much effort you put into it.

    Instead, why not file the edge flush to the sides, and install binding and purfling like a guitar? Depending on the width you would need, you could use double or triple line purfling, or if you need something wider, perhaps the checkered or diagonal pattern purfling strip [part # PFMQ4 from LMI] that is easily available.
    Yessir. Plan B is fire up the router and bind it conventionally. All sins disappear.

  15. #37

    Default Re: Back removal

    I mentioned earlier the purfling is in and would be in the way of conventional binding. And that would be too easy.

    I've been working on the back edges, and I think I can make it look acceptable (for a free instrument from a neophyte luthier). My son indicates he wants the mandolin regardless of miscues.

    Now, my next question will be asking for a finish schedule for the cherry back and sinker redwood top. I want to use varnish as practice for an upcoming violin.

    Thanks y'all - Gary

  16. #38
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    Default Re: Back removal

    The word "varnish" can mean almost anything these days.

    Traditional oil or spirit varnishes should be built gradually, with at least a full day's drying time between coats. Often, it is advisable to wait 2 or 3 days.
    If you use colors, double the drying time before putting anything over the color.
    Ditto for any sealing coats that have been applied over color.
    The instrument should be allowed to cure for 2+ weeks if you are going to rub out the final coat. It may be another 2 weeks before the instrument can be handled.
    Search the forums. The subject has been discussed within the last month.

    Practice on scrap more than twice.

    You can rout binding channels into the purfling, and cut a new purfling channel directly into the existing purfling. Cut it wide enough so the new purfling covers the old purfling. You don't have to take all of the old purfling out. Simply cut into it and choose a design that will completely cover anything that is left. We often see fancy guitars with borders that are as much as 1/4" wide.

  17. #39

    Default Re: Back removal

    Thank you for that. I think I'll just do my best to make it all look acceptable.

    I have reviewed dozens of threads about varnish in different fora. If I were using maple and spruce, I think I have enough information to move forward with varnish. But, without much forethought, I went with figured cherry and sinker redwood. Anyone finished either wood with OIL varnish?

    Gary

  18. #40
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    Default Re: Back removal

    I will suggest that you call International Violin Company and order their catalog. It contains some broad instructions on varnishing, and they sell all the supplies that you will need to seal and finish the instrument. You will also want to get some old-fashioned turpentine to use as a thinner and cleaner.

    The instrument will have to be sealed. They suggest a choice of their own bottled sealer, or very thin spirit varnish [a very thin solution of shellac and grain alcohol will work], or an old fashioned recipe for making your own sealer from gamboge. If you want to make it as easy as possible, just use their sealer.

    I don't know whether or not the variety of cherry that you are using is an open pored wood. If so, for best results, you will want to either use a pore filler, or use the old fashioned French polishing technique known as "loading." If it is not, you can just use a sealer and forget about filling or loading.

    Read up on sealing, filling, and loading. Make an initial choice and practice on scrap. Get a very good varnish brush, and keep it scrupulously clean. Gene Horner used International Violin's oil varnish on at least some of his mandolins.

    Oil varnish dries slowly. Depending on the weather and whether or not you thin the varnish, it may take anywhere from 2 to 5 days for a coat to cure before the instrument can be re-coated.
    Last edited by rcc56; Jun-21-2022 at 2:40pm.

  19. #41

    Default Re: Back removal

    Quote Originally Posted by GaryDavis View Post
    Thanks again for the advice.

    Is there some type of adhesive that does not darken the dust? Will varnish hold the dust in the oversized channel sections? Will the cherry dust darken like the solid wood does?

    Otherwise, I guess I'll try some wood putty (maybe) from the hardware store. Or not.

    I'm so conflicted here. Thanks for trying to help me sort this.

    Gary
    Rather then wood dust/glue or putty, you might see if there's a wood filler wax crayon that's close in color to your back wood. It's a little more work to get into fine cracks (I use a guitar pick) but it's color stays what it is, even with finish on it. be sure to seal the back before applying any filler or glue.

  20. #42

    Default Re: Back removal

    Maybe but an issue is starting with a very light colored cherry and having it darken over time. How would I know which color to choose when I don't know ultimately what color the cherry will become? I plan to briefly tan it in the sun. Maybe try something after that exercise?

    Thanks for your advice - Gary

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