Staining and sanding for a smooth surface while retaining color of stain - Woodworking Talk - Woodworkers Forum
 
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post #1 of 7 Old 06-04-2018, 07:53 PM Thread Starter
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Staining and sanding for a smooth surface while retaining color of stain

Here is my issue. I am going to stain and sand a (0.5mm) veneer. From my experience with stains, using a sandpaper no finer than 150 grit seems to yeld the best results when staining, but I want a very smooth surface ... sanded to at least 400 grit, or at most maybe 1000 grit. Going from 150 to 400 will remove a lot of color from the wood, this is my experience with water based stains at least.

I do not like wet sanding since I have had problem with pieces from the sandpaper getting stuck in the finish, but maybe this is cause i used a low quality sandpaper? However if I were to wetsand i guess i could add severall layers of stain and sand in between going from 150 - 320 - 400 and so on. I would get a deep color, but maybe this process would end up obscuring the burl and figure in the wood?

Anonther option would be to not sand the veneer with such a high grit (maybe just going to 280/320) and then add a layer of shellac, let it try and then use some FFFF pumice to grain fill and sand it smooth. When i got a nice smooth surface I then add more layers of shellac, and even thought the wood itself is just sanded with 280-320 grit this should not matter since i used pumice to fill the grain...

I got minimal experience with finnishing so I would appreciate some advice on this process. Anyways I will finnish the surface with shellac, and pumice for grain filling, im doing a french polish.
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post #2 of 7 Old 06-04-2018, 08:21 PM
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You shouldn't be sanding the wood after staining it. If you use a water based stain it will raise the grain and you would just have to live with a little roughness. An oil based stain wouldn't raise the grain so there woundn't be the need for sanding the stain.

Using water as a lubricant is pretty good for between the coats sanding of a finish but you have to use "wet or dry" sandpaper in order to use water.

Shellac is a type of finish that should be sprayed. You can get away with putting one coat on with a brush but after that the solvents in shellac will melt the dried finish so you are more likely to remove the previous coats of shellac with a brush than add coats.
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post #3 of 7 Old 06-04-2018, 08:56 PM Thread Starter
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You shouldn't be sanding the wood after staining it. If you use a water based stain it will raise the grain and you would just have to live with a little roughness. An oil based stain wouldn't raise the grain so there woundn't be the need for sanding the stain.

Using water as a lubricant is pretty good for between the coats sanding of a finish but you have to use "wet or dry" sandpaper in order to use water.

Shellac is a type of finish that should be sprayed. You can get away with putting one coat on with a brush but after that the solvents in shellac will melt the dried finish so you are more likely to remove the previous coats of shellac with a brush than add coats.

I have "researched" this on youtube, sanding the wood after staining is very common. Some stains wont do their work unless the grit is no finer than 150 and so you have to sand afterwards if you want a smooth surface. But I think i need to get a oil based stain as it seems that water based stain does not penetrate the wood anywhere near as good as oil based stain does, and therefore if I sand the layer of stain goes right off. I am considering mixing my dye in acetone, I think this will allow the stain to penetrate pretty deep and not raise the grain nearly as much as water.



I once stained pine and got a pretty smooth surface, the trick was to raise the grain with water and sand before staining. So when i applied to stain the grain did not rise.


Im using the old way of applying shellac by hand rubbing it it in (severall coats). I dissolve shellac flakes in 95% ethanol alcohol and rub it in with a ball of linen using a little bit of mineral oil to keep it smooth. But first ill grain fill it, Ill do this by applying a hand rubbed coat of shellac, let it dry, then mix pumice and alcohol and rub it in, that way the pumice will mix with fine saw dust and shellac and fill the pores of the wood allowing for a high gloss french polished surface.
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post #4 of 7 Old 06-04-2018, 09:21 PM
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Originally Posted by Tom Lilletveit View Post
I have "researched" this on youtube, sanding the wood after staining is very common. Some stains wont do their work unless the grit is no finer than 150 and so you have to sand afterwards if you want a smooth surface. But I think i need to get a oil based stain as it seems that water based stain does not penetrate the wood anywhere near as good as oil based stain does, and therefore if I sand the layer of stain goes right off. I am considering mixing my dye in acetone, I think this will allow the stain to penetrate pretty deep and not raise the grain nearly as much as water.



I once stained pine and got a pretty smooth surface, the trick was to raise the grain with water and sand before staining. So when i applied to stain the grain did not rise.


Im using the old way of applying shellac by hand rubbing it it in (severall coats). I dissolve shellac flakes in 95% ethanol alcohol and rub it in with a ball of linen using a little bit of mineral oil to keep it smooth. But first ill grain fill it, Ill do this by applying a hand rubbed coat of shellac, let it dry, then mix pumice and alcohol and rub it in, that way the pumice will mix with fine saw dust and shellac and fill the pores of the wood allowing for a high gloss french polished surface.
You can find all kinds of disinformation in youtube videos. Sanding stained wood is more likely to create a blotchy stain job regardless of what kind of stain you use or how it is applied. It's therefore unnecessary and undesirable to do any sanding in the finish until a coat of finish is applied.

You are right about the water based stain not penetrating. Chemically it's more similar to thinned down latex paint. It can be useful if a more uniform pastel appearance is desired though.

Rather than using acetone to mix a dye stain you would be better off using dentured alcohol. It's better for the dye and more compatible with the shellac you are using.

Raising the grain is a good idea with any wood when sanding. If you looked at wood through a microscope it would look like drinking straws glued together. When sanding it makes the ends of the grain fuzzy and when you raise the grain and sand with a finer grit it makes the ends cleaner. If you would raise the grain each time you go to a finer grit it would make the surface better and better so anything you might use that would tend to raise the grain when finishing would be minimal.

If you are going to apply shellac by hand apply it as quick as you can to prevent the alcohol from dissolving the previous coats. The thing about shellac is the dried flakes that you dissolve in alcohol to make a finish is the same stuff as the dried previous coats you have applied.
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post #5 of 7 Old 06-04-2018, 09:48 PM Thread Starter
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Originally Posted by Steve Neul View Post
You can find all kinds of disinformation in youtube videos. Sanding stained wood is more likely to create a blotchy stain job regardless of what kind of stain you use or how it is applied. It's therefore unnecessary and undesirable to do any sanding in the finish until a coat of finish is applied.

You are right about the water based stain not penetrating. Chemically it's more similar to thinned down latex paint. It can be useful if a more uniform pastel appearance is desired though.

Rather than using acetone to mix a dye stain you would be better off using dentured alcohol. It's better for the dye and more compatible with the shellac you are using.

Raising the grain is a good idea with any wood when sanding. If you looked at wood through a microscope it would look like drinking straws glued together. When sanding it makes the ends of the grain fuzzy and when you raise the grain and sand with a finer grit it makes the ends cleaner. If you would raise the grain each time you go to a finer grit it would make the surface better and better so anything you might use that would tend to raise the grain when finishing would be minimal.

If you are going to apply shellac by hand apply it as quick as you can to prevent the alcohol from dissolving the previous coats. The thing about shellac is the dried flakes that you dissolve in alcohol to make a finish is the same stuff as the dried previous coats you have applied.

Right, i was recommended to use acetone for my purposes by the manufacturer. They say it works better than water with their type of stain and it allows for deeper penetration than denatured alcohol (However I do find it a bit weird that they recommend acetone considering how "dirty" it is compared to denatured ethanol). Will it interact somewhat with the shellac finnish? i dont know, but i would think that if i leave the stain to dry for 1-2 weeks that any chemicals that might interact with the shellac-alcohol mix have evaporated. However I am not sure of this, but usually added additives evaporate in some weeks.



I guess i need to do some testing beforhand. Your right about the importance of alway keeping the shellac applicator moving, if you let it rest on the surface even just for a few seconds the alcohol will eat through the previous coats.

Last edited by Tom Lilletveit; 06-04-2018 at 09:53 PM.
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post #6 of 7 Old 06-04-2018, 10:35 PM
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Iíve never sanded stained wood unless I found a mistake I missed prior to staining. All sanding on the bare wood should be complete before staining.

The steps are:
1. Sand to a 220 but no more than 320 grit prior to staining
2. Apply stain
3. Apply finish
4. The finish can be flash sanded or scuff sanded between coats to assure a good adhesion for the next coat of finish and to assure a smooth surface
5. Apply finish (second coat)
6. If more than two coats of final finish is desired, repeat steps 4 and 5 until complete
7. The top coat can be rubbed out after the final finish has dried completely to get the amount of luster or shine you desire.

If you don't have time to do it right the first time, when will you have time to do it over?
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post #7 of 7 Old 06-05-2018, 12:07 AM
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Originally Posted by Tom Lilletveit View Post
Right, i was recommended to use acetone for my purposes by the manufacturer. They say it works better than water with their type of stain and it allows for deeper penetration than denatured alcohol (However I do find it a bit weird that they recommend acetone considering how "dirty" it is compared to denatured ethanol). Will it interact somewhat with the shellac finnish? i dont know, but i would think that if i leave the stain to dry for 1-2 weeks that any chemicals that might interact with the shellac-alcohol mix have evaporated. However I am not sure of this, but usually added additives evaporate in some weeks.



I guess i need to do some testing beforhand. Your right about the importance of alway keeping the shellac applicator moving, if you let it rest on the surface even just for a few seconds the alcohol will eat through the previous coats.
Acetone is just a lot hotter solvent. It will dry in ten minutes or so to where it won't be a problem with shellac. It's just that if you are applying the dye stain by hand the denatured alcohol will give you a little more working time.

The only time you might need to let a stain dry a week or more before putting a finish over the top would be to put a water based finish over an oil stain. Water based finishes are incompatible with linseed oil contained in oil stains. You can still short cut that by applying a single coat of a dewaxed shellac as a barrier coat before applying the waterborne finish.
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