What to do about shellac drying lines?

Discussion in 'Finely Finished' started by Yonatan, Sep 14, 2019.

  1. Yonatan

    Yonatan Tele-Meister

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    First finishing job. I applied and sanded off Z-Poxy twice and got a very smooth surface. Now I'm starting on the shellac finish, following a couple different YouTube series on FP.

    While I got a very nice gloss after the first session (which was just a seal coat, without adding alcohol at all to the pad, per one of the videos that I was watching), i also wound up with lines from the wiping strokes. They are very noticeable if you look closely, but hard to photograph. You can see them where the flash hit the body in the upper portion of the picture, or also at the glare at the very bottom.

    (These are not scratches that were filled with Z-Poxy, but lines created by the shellac strokes).

    Should I lightly sand with fine grade sandpaper (and wet or dry) to level things out, before proceeding with further sessions? Rub off with alcohol? Something else?

    And how do you avoid this, much less shellac (and perhaps always alcohol) on the pad when wiping it on?

    Edit: I'm using a 2 pound cut that I mixed from flakes. I just noticed that in the video I was following the seal coat was cut to 1 pound.

    shellac lines.jpeg
     
    Last edited: Sep 14, 2019
  2. eallen

    eallen Tele-Afflicted

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    Put on another coat to make sure there is enough thickness & then wet block sand with no finer than 400 using naptha. There is no avoiding lines of some degree with brush or wipe on in my experience. Otherwise people would choose wipe on instead of spraying for those who have a choice.

    Look forward to seeing pics of the progress!

    Eric

    Eric
     
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  3. Fretting out

    Fretting out Tele-Holic

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    You shouldn’t have to sand the next coat should melt in ,sounds like your shellac is too thick, you should cut it a little more and thin it out with a little more alcohol and apply it with a fine cloth with straight strides in thin layers

    Without being there it could be other things also , maybe someone will be able to give you some helpful advice here

    Good luck
     
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  4. LowCaster

    LowCaster Tele-Holic

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    I use a large soft brush (squirrel hair or that kind of thing), though any brush or even foam pad could do (except if the alcohol melts the foam). The less shellac the faster it dries, and the more brush strokes are visible. The only way to avoid those lines is to apply thick wet coats very fast, each new brush stroke blends, but then you end up with shellac dripping on the sides of the body. You need to sand eventually, and then finish again...

    Shellac works better for smaller objects or other application, or when you can deal with this problem.

    I don’t know z-poxy, but I guess it is a tough epoxy stuff? I don’t see the point of finishing with shellac over it. Shellac is thin and fragile, yes it is fast to apply with a brush, but the result is not perfect.

    You could try what Eric said, but because shellac layers are really thin once dry, it is not the kind of finish you want to use to build a thick layer and then sand and polish. That you can do with lacquer or poly. If you want to do it anyway, you should put on many coats, more like 3 or 6 (that’s only a few hours work).

    If you want perfect result with shellac you must learn « French polishing », and I don’t say that because I’m french! I don’t master this art myself, though I tried it, the learning curve is pretty steep. But the goal of French polishing is to build a shiny coat of shellac without any lines or visible strokes, and it is not easy.

    You could try clear lacquer (nitro). Spraying a few coats of lacquer is as fast as shellac and after two or three coats you can comfortably sand and polish.

    If you don’t want to spray, maybe you should try tru-oil or « wipe-on poly », those are easier, and tougher. The result is not as perfect or shiny as lacquer, but you can get a nice satin sheen that is quite comparable to shellac.
     
  5. maxvintage

    maxvintage Friend of Leo's

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    Shellac is great for this--are you putting a little oil on the pad?

    Shellac will dry really fast--like a couple minutes. You dont' have to sand it very often--the next coat will melt into the first coat. I typically wet sand every so often with 6 or 800 grit.
     
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  6. LowCaster

    LowCaster Tele-Holic

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    Sorry I just realized you are French polishing! I took those parallel lines for brush strokes.

    As I said I don’t master it. If I recall correctly, you can not avoid some lines in the first stages when you are building a coat of shellac. Then you sand, and you work more coats with less lines, and yes thinning with alcool is needed then. And at some point it goes wrong. Try to stop before that point.

    You need to experiment with the rubbing motion, which for me should be circular (moving circles and not strokes, though you could use very light strokes at some point), and the use of alcohol and oil, because the three are related and that’s the trick.

    Good luck and post pics please!
     
  7. Yonatan

    Yonatan Tele-Meister

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    Thanks for all of the responses. I'll try the suggestions mentioned.

    I originally chose shellac out of necessity, due to it's low toxicity, but I'm amazed at the initial results. Just need to work out the issues I'm having.

    progress.jpeg

    front.jpeg
     
  8. LowCaster

    LowCaster Tele-Holic

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    Yes it is a beautifull finish, and you are not doing too bad. This picture reminds me of my first build. You will be really amazed when you succeed.
     
  9. Macrogats

    Macrogats Friend of Leo's

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    That’s a nice looking guitar Yonatan. Please post progress pics.
     
  10. etype

    etype Tele-Afflicted

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    I am having the exact same issue! I am using a homemade pad and If you pull the pad off the edge, you end up with a good chance of a drip, but if you pull off before the edge you get a mark. You can see them and barely feel them, but they are there. I started with a 1 lb cut and have now thinned it down to maybe 3/4 lb cut. That helps a bit. Second, I am now working faster with less shellac on the pad (to avoid drips) and pulling my strokes off the edge. My plan is to build up several coats and then sand it flat (I figure more coats means I won't sand through). Then I'll do a couple more with an even thinner cut.

    Those of you who wet-sand shellac, would using mineral oil work? Or what else do you use? Naptha seems like it would evaporate too soon. How about Mineral Spirits?
     
    Last edited: Sep 15, 2019
  11. RodeoTex

    RodeoTex Poster Extraordinaire

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    Shellac doesn't build up very well.
    Maybe just get it to the color you want then coat it in lacquer.
     
  12. eallen

    eallen Tele-Afflicted

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    Great looking build Yonata! Keep the pics coming!

    I assumed from your original post you are using shellac as your top coat over z-poxy. If it is just a seal coat before a top coat you really don't need a seal or transition coat with z-poxy. I use Z-poxy as a pore fill and like it under nitro.

    Eric
     
  13. Yonatan

    Yonatan Tele-Meister

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    I had removed all of the Z-Poxy except for what's in the pores.

    Shellac is the main finish. I'm not set up to use chemicals that create nasty fumes. So I'm even using drinkable alcohol to mix and cut the shellac (well drinkable is debatable I guess, I wouldn't want to drink 190 proof alcohol!).

    I've thought about spraying a top coat (for protection over the shellac) of something clear from a spray can in the garage with the door open and wearing a respirator.

    But I might just leave it as all shellac, or possibly finish it off with bees wax or something.
     
    Last edited: Sep 15, 2019
  14. Silverface

    Silverface Poster Extraordinaire Ad Free Member

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    I recommend a few lacquer clear coats over it. Shellac has the lowest abrasion, impact and solvent resistance of any coating commonly used on guitars. It looks great when initially done but its limited durability fouls it up pretty quickly. That's why it's no longer used on production instruments - early in the 20th century most instruments in the violin family were shellac or varnish; ukuleles primarily shellac; and Weissenborn type instruments were coated with shellac.

    Nowadays, from a professional standpoint, clear (and orange) shellac are only used as restoration coatings for those instruments, not as new finishes.
     
  15. trapdoor2

    trapdoor2 Tele-Afflicted Gold Supporter

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    I agree that the lines are coming from attempting to put too much shellac down at once. After you've sanded down the pore filler, you should apply the first coat very simply and quickly as it is just there to start the process. I apply my 1st coat with a pretty sloppy-wet fad and just rub it in like I was applying filler or stain...but not leaving much on the guitar, there shouldn't be any hint of thickness, just coverage. It should flash off and be ready for the first FP coat in just 15min (assuming your room temp is comfortable).

    FP coats should be done with the standard cotton wool core wrapped in T-shirt material. I tried a bunch of other "quick and dirty" materials but building the correct fad made a lot of difference for me. Getting it loaded with shellac properly took some trial-and-error for me. Too much causes problems (like lines) and too little gets dry and sticky too quickly.

    At first, I didn't use mineral oil. I was unsure... However, it is needed and makes the process go really quickly. My first one, I think I sanded mine back to bare wood 3-4 times due to mistakes in the shellac process. I love it...so easy to fix or restart...and it just glows when it is right. It should be drying as you FP. When you get a couple of layers down, you'll be able to see a "comet tail" behind your fad as you polish. That's the alcohol flashing out as you go. I never spent more than 15-20min between layers during a session.

    I ended up with about 6 coats of shellac and then followed that with 2 coats of wipe on poly.

    Frankly, I don't think I'll do the poly on my own instruments anymore. I don't need that level of protection. I don't gig, etc. Lacquer and Poly finishes exists because they're fast, cheap and have more color choices. If you are about showing off the wood, it don't get much better than Shellac.
     
  16. Yonatan

    Yonatan Tele-Meister

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    I lightly sanded out the lines and started reapplying, being much more careful about not loading up the pad too much. After a few sessions, I'm starting to get a nice reflective gloss. I didn't include any oil yet, since I want to make sure that the wood is well covered before introducing oil. I'm starting to find a good rhythm in the process. What I really like is how flexible FP is e.g. if I only have 15 min, I can do a quick session, then throw the pad in a ziplock, come back later, etc.
     
  17. Silverface

    Silverface Poster Extraordinaire Ad Free Member

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    ??

    Shellac is faster and cheaper (per square foot, as applied) by far than lacquer or polyurethane.

    Lacquer and polyurethane are both far more durable and solvent resistant than shellac. Shellac may look pretty, but even if you play at home you run into situations that damage shellac finishes. I ony use them for historical restorations nowadays - too many problems with durability.
     
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  18. Yonatan

    Yonatan Tele-Meister

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    The back is getting nice and glossy. Here's the front after a few quick sessions:

    front few sessions.jpeg
     
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  19. trapdoor2

    trapdoor2 Tele-Afflicted Gold Supporter

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    A shellac finish takes too much time/effort for a production environment. Lacquer and poly get the product out the door, their durability is only a marketable side effect. INNSHO, it is all about the money.

    Durability is simply a question of ownership. Yes, shellac is not nearly as durable...but if you care for your instrument, durability becomes less of an issue. Shellac protected orchestral strings have handled centuries of gigs with minimal care. When they need touchup, it is insanely easy to do.

    I'm not saying that it should be used in every case. When I want to hide the wood (ie, use color), I'm going for poly. If I'm building something I think will be abused, I'm going for poly. If I want to show off the wood, give me a catalyzing oil and/or shellac.
     
  20. Silverface

    Silverface Poster Extraordinaire Ad Free Member

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    I can apply a full shellac finish on a body in less than 30 minutes total production time, including buffing. It's the easiest to apply and fastest (both in application and dry time) system available, making it ideal for a production environment.

    But durability issues are the problem. Yes, it's simple to touch up, but over time color shifts cause stark color contrasts between the original coats and touchups.

    Shellac was used on production lines in the early 1900's and was phased out when improved spray systems became available for lacquer application, as lacquer's physical strength and solvent resistance far surpassed/surpasses that of shellac.

    I'm curious where you got the impression shellac takes too much time and effort in a production environment, as that doesn't match the position of those of us from the coatings industry nor historical records of production line systems.
     
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