Here are the horrific pictures:
http://s47.photobucket.com/albums/f...urrent=114_1475.jpg&refPage=&imgAnch=imgAnch1
http://s47.photobucket.com/albums/f...urrent=114_1476.jpg&refPage=&imgAnch=imgAnch1
Well, what happens is that I initially applied a layer of shellac as wood conditioner. I then applied the all-in-one polyurethance+stain (walnut) but I think the polyurethane interacts with shellac that made everything looks kind of ugly.
What should I do now? Should I resand and apply shellac or reapply with some sort of polyurethane?
http://s47.photobucket.com/albums/f...urrent=114_1475.jpg&refPage=&imgAnch=imgAnch1
http://s47.photobucket.com/albums/f...urrent=114_1476.jpg&refPage=&imgAnch=imgAnch1
Well, what happens is that I initially applied a layer of shellac as wood conditioner. I then applied the all-in-one polyurethance+stain (walnut) but I think the polyurethane interacts with shellac that made everything looks kind of ugly.
What should I do now? Should I resand and apply shellac or reapply with some sort of polyurethane?
Interesting... I've seen shellac recommended to use as sealer before polyurethane but never tried it. I always used the final coat material, just thinned more.
What likely went wrong is
- you are applying a stain. This is supposed to penetrate and stain the wood. It will not work if you seal the wood with something else beforehand
and
- in addition, shellac will not polymerize but actually redissolve upon application of an appropriate solvent. That would explain the blotchiness.
Solution, sand thoroughly and apply the stain+PU coat directly.
In any case your coating will have instructions on the can I presume. I noticed that my results improved a lot when I started following these almost to the letter. There really is a difference between say, 10% and 20% dilution, when they tell you so...
Hope this helps,
What likely went wrong is
- you are applying a stain. This is supposed to penetrate and stain the wood. It will not work if you seal the wood with something else beforehand
and
- in addition, shellac will not polymerize but actually redissolve upon application of an appropriate solvent. That would explain the blotchiness.
Solution, sand thoroughly and apply the stain+PU coat directly.
In any case your coating will have instructions on the can I presume. I noticed that my results improved a lot when I started following these almost to the letter. There really is a difference between say, 10% and 20% dilution, when they tell you so...
Hope this helps,
Digital cameras never do justice: Is the bottom speaker treated same way - it looks much darker?
As MBK mentioned the stain won't penetrate the shellac and this prevents it from spreading evenly to the surface. Bubble marks, flowing stains or brush marks are usual symptons. If you, for some reason, have to apply a coating over (unsanded) shellac then the substance should actually be used undilluted and in fairly large amounts (to make sure the stuff spreads all over) ...and this has to be done FAST and on a flat surface to prevent flowing! (In case of a speaker cabinet you'd have to do one side at the time and let it dry before starting another one). Trying to patch lighter areas during the process usually leaves gigantic brush marks and does more harm than good. Patching them when the coating has dried will leave dark stains. The idea to success is to apply an even surface at ONCE and never touch it again. This is a tricky technique and hard to master - I have managed to do it sufficiently for few floor- and door strips but never would do it for larger surface areas, such as speaker cabinets since I don't have the skills for it. The usual order of applying shellac over a stained wood is much easier.
You could try either lightly sanding the cabinet (a coarse surface will absorb the coating better) or alternatively fully remove both layers (coating and shellac). The latter requires a lot of work: You have to make sure all the shellac is actually gone since the wood absorbs it as well but probably the end result is better.
As MBK mentioned the stain won't penetrate the shellac and this prevents it from spreading evenly to the surface. Bubble marks, flowing stains or brush marks are usual symptons. If you, for some reason, have to apply a coating over (unsanded) shellac then the substance should actually be used undilluted and in fairly large amounts (to make sure the stuff spreads all over) ...and this has to be done FAST and on a flat surface to prevent flowing! (In case of a speaker cabinet you'd have to do one side at the time and let it dry before starting another one). Trying to patch lighter areas during the process usually leaves gigantic brush marks and does more harm than good. Patching them when the coating has dried will leave dark stains. The idea to success is to apply an even surface at ONCE and never touch it again. This is a tricky technique and hard to master - I have managed to do it sufficiently for few floor- and door strips but never would do it for larger surface areas, such as speaker cabinets since I don't have the skills for it. The usual order of applying shellac over a stained wood is much easier.
You could try either lightly sanding the cabinet (a coarse surface will absorb the coating better) or alternatively fully remove both layers (coating and shellac). The latter requires a lot of work: You have to make sure all the shellac is actually gone since the wood absorbs it as well but probably the end result is better.
At the top, it appears that glue has saturated the wood and added it's effect. Additionally it appears that the shelac is on the surface rather than into the wood fibers, where you want it.
Did you cut the shelac before application? Usually woodfinishers go for a 1/4 pound cut or 1/6 pound cut; meaning a 4:1 or a 6:1 mix of pure alcohol. This of course assumes shelac from a can... which has a very limited shelf life. Best results are to be had when you mix your own shelac from flake.
Having pointed that out, I would think some time spent with a sandpaper and a flexable cabinet scraper are in order. Cabinet scraper is likely to be your best friend. Take some time to learn how to condition the edge of a scraper (file, dress, burnish). Good source (maker) pretty much worldwide of such a tool is Sandvik
Cyclotronguy
Did you cut the shelac before application? Usually woodfinishers go for a 1/4 pound cut or 1/6 pound cut; meaning a 4:1 or a 6:1 mix of pure alcohol. This of course assumes shelac from a can... which has a very limited shelf life. Best results are to be had when you mix your own shelac from flake.
Having pointed that out, I would think some time spent with a sandpaper and a flexable cabinet scraper are in order. Cabinet scraper is likely to be your best friend. Take some time to learn how to condition the edge of a scraper (file, dress, burnish). Good source (maker) pretty much worldwide of such a tool is Sandvik
Cyclotronguy
From the pictures, I would assume the cabinets are constructed of veneered MDF. Sanding them down will probably result in sanding right through the veneer, particularly around the corners of the cabinets. If my assumption is correct, have you considered chemically stripping the cabinets, light sanding with 220 grit and then painting them?
soufiej said:
The cabinets are veneered. I probably need to use some sort of chemical to remove the poly. ahh ...
IIRC this is the same stuff that Chris used on the latest Frugel-Horns. Never again.
Except where the finish bunched up & dried into dark opaque spots i rather like the copperish finish that came out thou...
I've alerted Chris to this thread, maybe some ideas can be shared.
dave
Except where the finish bunched up & dried into dark opaque spots i rather like the copperish finish that came out thou...
I've alerted Chris to this thread, maybe some ideas can be shared.
dave
Yep, I definitely found the "all-in-one" poly stain/finish to be a absolute PITA to work with. My preference is wipe on oil or alcohol based stains, followed by sprayed catalyzed nitro cellulose lacquer. On small jobs, I've had wonderful success with the Mohawk brand nitro lacquer spray bombs (35 sheen my favorite) - other locally available name brands might suffice.
The only reason I even tried the former was very difficult to reach small open compartments in the FrugelHorns.
Even with appropriate "pre-conditioning", I found the poly very uneven and shallow on grain penetration; but more frustrating was the short open time before tacking up - very hard to brush or wipe a large area without streaking, clumping, and running( most particularly at edges).
While I don't usually seal with the shellac before the stain, and can't speak from experience, I don't think the shellac was the problem; but from my recent "adventure" with poly, I can advise that light sanding and reapplication won't solve the problem either.
When a project goes this bad for me, I usually chemically strip the offending finish and random orbit sand the veneer 'til I see only sawdust. Sometimes that means a sand through and need to reveener.
just for "fun":
http://en.wikipedia.org/wiki/Polyurethane#Varnish
The only reason I even tried the former was very difficult to reach small open compartments in the FrugelHorns.
Even with appropriate "pre-conditioning", I found the poly very uneven and shallow on grain penetration; but more frustrating was the short open time before tacking up - very hard to brush or wipe a large area without streaking, clumping, and running( most particularly at edges).
While I don't usually seal with the shellac before the stain, and can't speak from experience, I don't think the shellac was the problem; but from my recent "adventure" with poly, I can advise that light sanding and reapplication won't solve the problem either.
When a project goes this bad for me, I usually chemically strip the offending finish and random orbit sand the veneer 'til I see only sawdust. Sometimes that means a sand through and need to reveener.
just for "fun":
http://en.wikipedia.org/wiki/Polyurethane#Varnish
Bad Finish
From the look of it, it does appear that the biggest part of the problem is the use of tinted (all-in-one) poly varnish. Throw it out. It's nearly impossible to get perfectly even coverage with brush-on finishes, especiially on vertical surfaces. Tinted varnish just magnifies the problem. You can see where brushing near the corner has squeegeed finish off the brush, leading to uneven, drippy-looking coverage.
Cyclotronguy is right on about the cabinet scraper. It should be able to take the varnish off to the point you can sand down pretty much to bare wood--do be careful on the corners, as they'll wear down first.
Personally, I stay away from chemical strippers (especially methylene chloride), as they take all the luster out of wood and leave it looking like cardboard with grain. If you've veneered it yourself, it may also melt the veneer glue.
When you get the finish off, use a good wood stain applied with a rag. You may need a couple of coats. On absolutely bare, pristeen wood I have had great results with alcohol-soluble dyes, which really stain the wood instead of smearing it with pigment as oil stains do. However, I expect you're better off here with oil stain.
When varnishing, put on the thinnest even coat you can manage. Let it dry thoroughly, sand lightly w/220 or 440 grit paper, then apply a second coat. Lather, rinse, repeat. I think it doesn't start to look really right until about coat #4. Finish the top coat with a bit of paste wax.
Hope this helps,
--Buckapound
From the look of it, it does appear that the biggest part of the problem is the use of tinted (all-in-one) poly varnish. Throw it out. It's nearly impossible to get perfectly even coverage with brush-on finishes, especiially on vertical surfaces. Tinted varnish just magnifies the problem. You can see where brushing near the corner has squeegeed finish off the brush, leading to uneven, drippy-looking coverage.
Cyclotronguy is right on about the cabinet scraper. It should be able to take the varnish off to the point you can sand down pretty much to bare wood--do be careful on the corners, as they'll wear down first.
Personally, I stay away from chemical strippers (especially methylene chloride), as they take all the luster out of wood and leave it looking like cardboard with grain. If you've veneered it yourself, it may also melt the veneer glue.
When you get the finish off, use a good wood stain applied with a rag. You may need a couple of coats. On absolutely bare, pristeen wood I have had great results with alcohol-soluble dyes, which really stain the wood instead of smearing it with pigment as oil stains do. However, I expect you're better off here with oil stain.
When varnishing, put on the thinnest even coat you can manage. Let it dry thoroughly, sand lightly w/220 or 440 grit paper, then apply a second coat. Lather, rinse, repeat. I think it doesn't start to look really right until about coat #4. Finish the top coat with a bit of paste wax.
Hope this helps,
--Buckapound
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