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A few questions about varnish finish

Discussion in 'Luthier's Corner' started by Swever, Apr 16, 2009.


  1. Swever

    Swever

    Nov 13, 2008
    Joensuu, Finland
    So, I'm about to start finishing my first build really soon.

    I decided to use varnish, since the wood I use (aspen) is very soft. I bought this stained varnish (it should be polyurehtane), expecting it to stain the wood more evenly than a thin stain would.

    i-113.

    That must be partly true, but I'm still not fully satisfied with the results so far.

    Here is the first coat. Mixed with white spirit 50/50

    i-117.

    i-118.

    The second coat. About 20% of solvent added.

    i-124.

    i-125.

    It's obvious that it gets better, but I'm not sure if it will give satisfactory results after more coats. Yea, this scrap piece was not sanded properly before applying the varnish, but it seems not to be the main reason anyway.

    The finish looks somewhat dirty... Is that because of poor sanding? Or is it normal for stained varnish to look like that? Would it get better after more coats, what do you think?

    Perhaps I should use some sealer before applying this thing? What should I better use as a sealer? This Liberon Bistrot Varnish (Hardwearing Varnish) is also available in clear, and I can also use it as a top coat. There's also Liberon finishing oil available here. Though these things are quite expensive here, so maybe there are some cheaper options? I hear white glue mixed with water is used as a sealer, not sure if it would work with this solution though.

    OK, sorry, too much questions. To sum it up:

    1) Do I need a sealer?
    2) Do I need a clear top coat?
    3) What should I use as sealer?


    And one more thing that's not absolutely clear to me. How do I apply the finish? Should I cover the whole body in one go, having it suspended as when sprayed, or should I cover one of the surfaces at a time and keep it on a table?

    I'm so confused with all this finishing! :help:
     
  2. 62bass

    62bass

    Apr 3, 2005
    It's best to do your research on finishing before deciding on what finish you buy. But, you're already started so you had best carry on to avoid more expense.

    What you have is a varnish with a pigment stain in it. How dark it gets will be determined by how rough the wood surface is, type of wood (close grained like alder or maple or open grained like oak and ash) and the number of coats you apply. The dirty look, judging by your picture, is probably caused by rough sanding, open grained wood and the nature of the pigmented varnish. Personally, I don't like using that stuff if I decide on a varnished surface and want to colour the wood. I prefer using either a wood dye or a wipe on stain, then top coat with clear gloss varnish, which I can finally either steel wool to a satin finish or rub out to a gloss.

    What I'd do is sand the body very smooth now, starting with about 120 grit sandpaper and working up through the grits to about 320. Wipe off all the sanding dust before changing grits. Then examine your work carefully to make sure you didn't miss anything. If it's perfect, brush on an even coat of your Liberon with a brush (disposable foam brushes are okay) covering the entire body before any part of it starts to dry. Don't put it on so thick that it runs or drips. Practice on scrap wood first. You might want to thin it with solvent about 10%.

    When thoroughly dry look at it and decide if it's dark enough. If not, sand lightly (very lightly) with 400 grit paper and apply another coat and let it dry. When it looks right sand the final coat very smooth with 400 grit working very lightly and be careful you don't cut right through the stain to bare wood. This can easily happen on the rounded edges. On rounded edges I often use steel wool or a synthetic finishing pad, fine grit.

    When it's nice and smooth and even, switch to a clear gloss varnish for the top coats. You can use Liberon. Apply a coat, let dry and sand (again very lightly) with 400 grit just enough to remove any rough nibs. Wipe off all sanding dust and apply more coats sanding lightly with 400 grit between each coat as before, until you have the finish as deep as you want. If the wood is a very coarse grain, like ash, you'll probably never get it completely filled. But you will still get a good final result. I'm not familiar with aspen.

    When it's decided that it's as good as it's going to get, let that final coat dry for a couple weeks in a warm room.

    Then, since it's a polyurethane (we think), and paint store grade poly is terrible to rub out to a mirror gloss, you'll have to go for a satin look. Sand very lightly with 600 grit and wipe off the dust. Then with 0000 (finest grade) steel wool (Liberon brand is the best), rub the surface evenly to an even satin finish, wipe off the dust and wax it with a furniture paste wax and a soft cotton cloth. Liberon makes some good furniture paste wax. You'll get a pretty nice, warm and not too shiny, but very appealing, semi gloss surface that glows and feels great.

    If you have some larger pieces of that aspen handy, practice on it first before starting on the bass, going through the entire series of steps above. You'll learn a lot and it'll help when you do it for real on the bass.

    I wouldn't use a sealer under a pigmented varnish. I wouldn't use glue for a sealer. If I used a sealer I'd put it on top of the stain or dye. De-waxed shellac makes a good sealer. Also a thinned out coat of the varnish will do well as a sealer. I only use a sealer in cases where I want to prevent the finish coats from dissolving the stain or dye and getting weird looking. Using what you're using you won't have that problem if your first stain coats are dry.

    There are other finishes you could have used that would be easy for a beginner, such as an oil finish, like tung oil or linseed oil. They can look good. They're easy but take just as long to do it right. A wipe on varnish, such as Minwax Wipe On Polyurethane, is easy and gives a decent semi-gloss finish. Tough to hand rub to a mirror sheen though. If I used that and wanted to colour the wood, I'd stain it with a gelled wipe on stain or dye it with a water based dye before putting on clear top coats.

    They all have their supporters and critics.

    If you need more help from me, just ask. Others will chime in probably with more suggestions. Some of them will be helpful and some will be silly. It'll depend on how much experience the person posting has.

    Hope this is of help to you. Good luck with it.
     
  3. Swever

    Swever

    Nov 13, 2008
    Joensuu, Finland
    First of all, thank you very very much, sixtytwo!

    Now I have explain my choice of stained varnish. Aspen is extremely absorbent, just like paper. I guess it absorbs more that pine. That's why I was sure (and still am) that any water-thin stain or dye would work even worse in this case. I thought that a thick varnish would give an even colouring, but it turns out it still soaks too quickly and unevenly into the wood. That's why I suppose that a sealer, or conditioner, or however this this thing is called, should solve the problem.

    The other problem is that it appears that bistrot varnish is not available in clear here :(
    So I have to choose either Liberon finishing oil or something else. I'm leaning towards the finishing oil if there would be no compatibility issues, since, i guess, it should give a bit more protection and isolation from environment humidity. Am I right?
     
  4. 62bass

    62bass

    Apr 3, 2005
    I understand. I'm not familiar with Liberon finishing oil, but it sounds like one of the oil/varnish blends which give a finish similar to tung oil.

    It should be easy enough to apply, but is not meant to be applied over any type of sealer or primer. To bare wood only. I wouldn't even put it over a conditioner. You put on multiple coats, wiping off the excess before it dries until you get the desired finish. They can't be built up to a thick finish. It's an "in the wood" type finish. But it should look good.

    You can try a stain underneath to colour the wood but you definitely don't want one that seals the wood and most of them do.

    I'd say, experiment on scrap first.

    Blotching of stains and dyes on wood is something I do run into. A conditioner can help that as can choosing the right stain. Gelled stains work best for less blotching. I sometimes use a combination of a dye followed by a gelled stain. But that's under a varnish type finish that is meant to sit on top of the wood.

    As I said, practice on scrap first until you get something that works.
     
  5. Swever

    Swever

    Nov 13, 2008
    Joensuu, Finland
    Sorry, I did not make myself entirely clear. I meant to use this "Finishing Oil" itself as a sealer under the stained varnish. The side effect, but a beneficial one, would be that the finish is both in-the-wood and on-the-top. This, I suppose, should give better protection than just varnish alone.

    I'm pretty sure that it should work this way. I think I'm going to try this method.
     
  6. Swever

    Swever

    Nov 13, 2008
    Joensuu, Finland
    And yea, you mentioned that the whole body has to be covered in one run. Does this mean that I should hang it vertically? Would not this cause irregular thickness of the finish, especailly the later varnish coats?
     
  7. 62bass

    62bass

    Apr 3, 2005
    That should work fine. Practice first though. I'd wipe on the finishing oil with a paper towel so it goes on evenly and doesn't pool up.
     
  8. 62bass

    62bass

    Apr 3, 2005
    It can if you put it on too thick. What I did is I made a "rotisserie" set up to hold bass bodies horizontally at the neck cavity and the end pin hole. I can rotate the bass quickly with my left hand as I brush or wipe on a finish and then turn it to a flat position until it dries. I'm sure you could design something like that for yourself using scrap 1"x4" wood and a few wood screws. Instead of using a flat piece of wood for a handle to hold the bass at the neck cavity I used a length of 1 1/2" dowel with a flat piece and some appropriate size screws to fit into the holes for the neck screws. That's okay for bolt on necks. I just leave the thing attached until finishing is done and I can still hang the bass up by the dowel to get it out of the way. I clamp the base of this jig in my Workmate or to my work bench. However, that may be not necessary for you. I just made mine because I was bored for one thing and it made things very convenient for quickly wiping on coats of a thinned out and extremely fast drying varnish I sometimes use. This varnish dries to the touch in minutes, almost as fast as lacquer, and can be sanded level for the next coat in 2 hours or less. No chance of runs or drips using it, but you have to be able to work very quickly to avoid application marks and build up where each pass overlaps the previous one.

    Anyhow, that's why it helps to practice first. Then you can see if you need to thin the varnish some and how it applies and how much you need to put down each coat.
     
  9. Swever

    Swever

    Nov 13, 2008
    Joensuu, Finland
    Thank you very much once again! A rotisserie sounds like a great idea. Probably I will make something like that.
     
  10. I use a cut off broom stick about 18" long with two holes drilled in it so it can be bolted to the body's neck pocket. The round handle allows me to hold it, rotate it, move it up or down as necessary. It also has an eyelet screw in the end so I can hang it to let it dry. I am an advcate of using several light coats instead of few heavy coats. I use True oil and apply it with my fingers and burnish as I apply it. If anything, it dries too fast yet I still let it dry for several hours before appling the next coat. I use 0000 steel wool between coats but the last coat is burnished/polished with the palm of my hand or fingers.
     
  11. Swever

    Swever

    Nov 13, 2008
    Joensuu, Finland
    Just in case.. Is there any wood putty that would accept oil and varnish over it?
     
  12. 62bass

    62bass

    Apr 3, 2005
    Most will accept a finish over them, even an oil varnish mix. However, they'll show up as an obvious patch because the finish doesn't absorb the same as wood and the surface is different texture. If you can dye the patch to very closely match the surrounding wood, it won't be as obvious. Some wood putties can be tinted with dry artist's colours. I don't know what you have available there so I can't give much advice. I have a whole bunch of tricks I resort to when refinishing wood, but I know what materials to use and where I can buy them locally.The best way to get an invisible repair is with a patch cut out of matching wood. That requires a bit of work and skill and even then it might show a bit although I've done some that only I can find with difficulty.
     
  13. Swever

    Swever

    Nov 13, 2008
    Joensuu, Finland
    Thank you for such a quick and full answer!
     

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