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Thread: Refinishing Options

  1. #1

    Default Refinishing Options

    When building a kit mandolin what are some of the benefits of various refinishing options, assuming there is generally more than one option?

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    Registered User Bill Snyder's Avatar
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    Default Re: Refinishing Options

    What do you need to refinish. This is a new build so there is no refinishing.
    Bill Snyder

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    Default Re: Refinishing Options

    Quote Originally Posted by Bill Snyder View Post
    What do you need to refinish. This is a new build so there is no refinishing.
    I guess I meant finishing? Are kit mandolins already painted/stained?

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    Default Re: Refinishing Options

    There is much to learn about finishes. Your options include shellac, varnish, lacquer, polyurethane, and oil. Here are some advantages and disadvantages of each.

    Shellac is a natural product from insects and is easy for a beginner if you brush it on. It is also forgiving. You should not use hardware store shellac in a can. Dry flakes fresh mixed with alcohol works much better because as an organic product it does have a shelf life. Some use a French polishing technique with shellac that requires a learning curve but gives a shinier finish. If you don't use the French polish technique shellac's look is a soft gentle luster. Shellac is not as hard as some other finishes. It is also often used as a first coat sealer for other finishes because practically anything sticks to it.

    Varnish is made from natural and/or synthetic resins and takes time to do right. Spirit varnish dries more quickly but that actually makes it harder to use. Oil varnish gives you much longer drying time but also more time to work and self level. A proper varnish job takes at least a couple of months. Multiple coats are needed and each one must be completely dry before rubbing out for the next coat. The rubbing out steps are crucial because the bond between coats of varnish is physical not chemical and each new coat needs "teeth" to grab on to.

    Lacquer is made from nitrocelluose and is a very traditional choice. Wood is largely cellulose chemically speaking so it adheres to wood very well. Lacquer gives a hard and durable protective finish. Each coat melts into the previous coat because of the solvent. This also makes lacquer easier to repair. Spraying gives the best results, so you need spray gun equipment. You can get rattle can lacquer instead. Brushing formulas work but require a lot more effort rubbing out. The solvents used in lacquer and its thinner are highly toxic. Some companies offer water based lacquers (not nitrocellulose) that are not as toxic.

    Polyurethane is actually a variety of varnish with a synthetic "plastic" resin base. It is available in brushing and spraying formulas. It is relatively easy to use and makes a very durable "bulletproof" finish. Some claim it kills tone but this is disputed. One thing is certain: its durability is a liability if it ever needs to be refinished or repaired. Impervious to many solvents, physical removal by abrasives or heat is often the only option.

    Wipe on oil finishes such as Tru Oil (used on gun stocks) are popular with amateur instrument makers because they are virtually foolproof. Wipe on, let dry, rub out, and repeat until you get the look you want. Tru Oil specifically consists of linseed and other oils, solvents, and drying agents. Many of us on the Cafe have had very good results with Tru Oil. And it is easily found at your local Wal Mart or sporting goods store.

    Some finishes are hybrids. It is common to find wipe on varnishes for example with a significant oil component. Formby's Tung Oil Finish is an example of that. It is really a wiping varnish that includes oil.

    Kit instruments are not pre-finished. When you see how many choices there are this would indeed be foolish. People are very individual about their finish choices. Not only what type of finish but there's color too. Natural? Tinted? Sunburst? And what level of gloss? Full gloss? Semi gloss? Satin? Matte? This is why kit manufacturers leave the finish choice to the builder.

    I recommend you use the search function on the Forums to search for finishing threads. There are many and you can learn a lot. Maybe pick up some books. I've heard Stew Mac's "Guitar Finishing Step By Step" is a good one and on sale right now I think. Frank Ford's Frets.com Web site has some finish information.

    After having built a few kits and also having done a few instrument restorations I can honestly say that finishing is the hardest part. By far. Many of the professional builders who hang out here would agree I believe. A couple more thoughts: whatever you choose keep it THIN. And the cardinal rule if you are new to finishing (or even experienced but trying something new)- and I am capitalizing it not to be rude but because it is that important- PRACTICE ON SCRAP FIRST! Most of us, me included, learn that the hard way! I hope all this helps.
    Last edited by multidon; Nov-27-2013 at 7:09pm.
    Don

    2016 Weber Custom Bitterroot F
    2011 Weber Bitterroot A
    1974 Martin Style A

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    I may be old but I'm ugly billhay4's Avatar
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    Default Re: Refinishing Options

    For a kit, I also suggest Tru Oil for the same reasons as Don said. And, if you stain, make sure it will not bleed under the oil.
    Practice.
    Bill
    IM(NS)HO

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    Registered User Bill Snyder's Avatar
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    Default Re: Refinishing Options

    All lacquers are not nitrocellulose though instrument lacquers generally are. Also most if not all manufacturers recommend a sealer of some sort before applying them in part to avoid adhesion problems.
    As far as shellac goes I have used it on the handful of instrument I have built and I can't imagine using a brush to apply it. I know that some people do large pieces with a brush but I think using a cloth has to be much easier. The other option is to spray it. You could mix your own and spray it with a Preval sprayer.
    As far as needing to mix it yourself read THIS from Frank Ford's Frets.com website. This is the product I used on this mandolin and I applied it with folded up paper towels. This mandolin is almost 9 years old and it still looks just like this.

    Click image for larger version. 

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    Bill Snyder

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    Registered User Nick Gellie's Avatar
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    Default Re: Refinishing Options

    Bill, your mandolin has a fantastic natural look after 9 years using shellac polish. I like the idea that it is a natural product and not a nasty smelling finish compound like nitrocellulose. How well does the shellac adhere to a stain underneath? Any issues to watch out for?
    Nic Gellie

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    Registered User Timbofood's Avatar
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    Default Re: Refinishing Options

    Gee Don, that was a nice little primer about finishes. It will, hopefully spur GreGooch on to building something he will be proud of!
    Good luck
    Timothy F. Lewis
    "If brains was lard, that boy couldn't grease a very big skillet" J.D. Clampett

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    Registered User Bill Snyder's Avatar
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    Default Re: Refinishing Options

    Nic, shellac generally adheres as well as any other finish available. Dewaxed shellac is known as the universal primer because it sticks so well and is compatible with most other finishes. This means it makes a great seal coat or can be used on top of most other finishes. There are some of the new, "super" finishes it does not work with though.
    Bill Snyder

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    Default Re: Refinishing Options

    Bill I am glad you brought up the Preval sprayer. Its a great option. Of course you can buy shellac in a rattle can but no way to know how fresh it is.

    You are right that brushing isnt the best option for shellac but it is easy for a beginner. I have done it and ended up sanding a bunch off to get rid of brush marks. The best application method I found is to use a "tampon" basically a wadded up cloth inside another cloth. Its the bomb for Tru Oil as well. Even though I already warned against hardware store shellac because of the freshness issue I wanted to say that some here have said they did ok with Zinsser (?) Bullseye brand. However its "cut" is too thick. Should be thinned 50/50 with denatured alcohol.
    Don

    2016 Weber Custom Bitterroot F
    2011 Weber Bitterroot A
    1974 Martin Style A

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    Registered User Nick Gellie's Avatar
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    Default Re: Refinishing Options

    Quote Originally Posted by Bill Snyder View Post
    Nic, shellac generally adheres as well as any other finish available. Dewaxed shellac is known as the universal primer because it sticks so well and is compatible with most other finishes. This means it makes a great seal coat or can be used on top of most other finishes. There are some of the new, "super" finishes it does not work with though.
    Yes, so it is best to get dewaxed shellac or decant shellac in liquid form once the wax has settled to the bottom. Good to know that it is used as a universal primer. I would go with Multidon's suggestion as well to use a cloth inside a cloth to get the best result. I would also try some out on a test piece of wood before applying it so that one gets an idea how one's application is going.
    Nic Gellie

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    Registered User Max Girouard's Avatar
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    Default Re: Refinishing Options

    When we started learning how to use KTM-SV, we followed the handout that Rolfe was using for applying the finish. If your interested, here is a link to a write up Rolfe did a few years back. We really like it and almost all our instruments are finished with it. We spray, but it can also be brushed on, and it levels out really nice. The only downside, is that it doesn't repair as well as shellac or nitro. You'll also need a nice buffing setup as buffing out by hand can be a real chore.

    http://www.newenglandluthiers.org/co...ed_finish.html

    Since the article was written, he has been using Zinsser Sealcoat for sealing the wood (rather than using the Target Shellac) after the dyes and airbrushed dyes are applied. You have to make sure that you use the Sealcoat and not the can that is just labeled shellac. The sealcoat is made of de-waxed shellac where as the plain shellac still has the wax in it, which could lead to finish problems. There is a code printed on the lid of the can which will tell you the year and month it was made so you will want to use something made in the last 6 months. I don't have my code key with me now, but if I remember correctly, the first numerical digit is the year and the second is the month. Besides myself and Rolfe, I know of 4 other builders who use Zinnser sealcoat without problems. I used to buy and dissolve my own shellac, but after a bunch of testing of the sealcoat vs. our own dissolved flakes, I found the sealcoat to be a better solution for us.

    The sealcoat comes in a 2lb cut which is the pound cut that is recommended for bodying sessions during French polish according to the Millburn method of French polishing (http://www.guitarsint.com/article.cf...cleContentId/8), so you can use it straight from the can and then thin out 50/50 for the last sessions. I've used it for French polishing, and it worked great. The Zinnser shellac comes in a 3lb cut which is too thick, but you don't want to use that due to the wax issue. We've also brushed in on full strength with a natural bristle brush, but you must move quickly and not go over any areas that have dried, which can be a matter of seconds.

    For the instruments that we will be finished with KTM-SV, we spray it without thinning. I can't imagine spraying it with our setup any thinner as it would run and possibly move the color. But with that being said, every ones technique and equipment will be different so you'll have to experiment what will work best for you.

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