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Hello- wondering if anyone has had a similar experience or can offer guidance. I applied a medium walnut Watco Danish oil finish over tropical walnut with some wet sanding. Let dry 3 days and color was beautiful. To ensure all pores filled (looking to achieve glass-smooth finish) I used Varathane sanding sealer next. But, it dried somewhat milky in spots and did NOT sand out cleanly- essentially left a white, ground-in residue over entire surface and in spots actually dissolved/diluted the darker danish oil color out. Ruined the piece and am now sanding down to bare wood. Is this a known incompatibility? Thanks for any tips!!
 

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The Nut in the Cellar
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I've never used a sanding sealer over a finish and haven't heard of that technique being used either. Normally, one fills the grain of the wood with filler or sealer tinted to match the wood. Then you can do the finish. I've used Watco Danish oil for decades under varnishes with no issues. However, I usually let the Danish oil cure for a week (or in a warming box) to ensure it has fully absorbed into the wood and cured. I suspect the sanding scuffed the not fully cured oil finish and combined with the water based sanding sealer dust to produce the cloudy stuff. The oil can lie in the pores of the wood and cure very slowly. It may feel cured, but not be in the pores of the walnut. If this were my piece, I'd apply two applications of the Danish oil, allowing full curing before topcoating with any finish. My preferred topcoat would be a wipe on varnish, scuffing between applications until I had achieved the build of finish desired.
 

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Not sure what the chemical composition of watco is but generally a Danish oil finish is a mixture of linseed oil and tung oil. If it has tung oil in it that could be the culprit. Tung oil is a very slow drying finish and even though you let it dry three days that may not have been enough. It's not that the watco was incompatible, it just needed to be completely dry.

For what you were doing you used the wrong products. The open grain of walnut should have been filled with a pastewood grain filler. The watco wasn't needed. You could have went straight from grain filler to sanding sealer.

The good news is it shouldn't be difficult to remove the sanding sealer by wiping it down with lacquer thinner. Then if you allow it to dry well you could still use a grain filler. Mohawk Finishing Products makes a walnut grain filler that is walnut color like the wood. Sherwin Williams makes a good grain filler but it only comes in a natural color. You can have them tint it for you though. If you do that have them tint it a very dark brown.
 

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Discussion Starter #5
I've never used a sanding sealer over a finish and haven't heard of that technique being used either. Normally, one fills the grain of the wood with filler or sealer tinted to match the wood. Then you can do the finish. I've used Watco Danish oil for decades under varnishes with no issues. However, I usually let the Danish oil cure for a week (or in a warming box) to ensure it has fully absorbed into the wood and cured. I suspect the sanding scuffed the not fully cured oil finish and combined with the water based sanding sealer dust to produce the cloudy stuff. The oil can lie in the pores of the wood and cure very slowly. It may feel cured, but not be in the pores of the walnut. If this were my piece, I'd apply two applications of the Danish oil, allowing full curing before topcoating with any finish. My preferred topcoat would be a wipe on varnish, scuffing between applications until I had achieved the build of finish desired.
Thanks Jim!
 

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Discussion Starter #7
Not sure what the chemical composition of watco is but generally a Danish oil finish is a mixture of linseed oil and tung oil. If it has tung oil in it that could be the culprit. Tung oil is a very slow drying finish and even though you let it dry three days that may not have been enough. It's not that the watco was incompatible, it just needed to be completely dry.

For what you were doing you used the wrong products. The open grain of walnut should have been filled with a pastewood grain filler. The watco wasn't needed. You could have went straight from grain filler to sanding sealer.

The good news is it shouldn't be difficult to remove the sanding sealer by wiping it down with lacquer thinner. Then if you allow it to dry well you could still use a grain filler. Mohawk Finishing Products makes a walnut grain filler that is walnut color like the wood. Sherwin Williams makes a good grain filler but it only comes in a natural color. You can have them tint it for you though. If you do that have them tint it a very dark brown.
Thanks Steve. I was using the Watco to impart some color, but also wet sanding it to fill the grain. I should have just avoided the Varathane sealer altogether. Good news I was able to sand it back to original state. So we'll give it another go :)
 

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The Nut in the Cellar
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Some folks have wet sanded the Danish oil to create a filler slurry. This is left to cure and then finish sanded if the grain is filled.
 

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The white could have come from the wet sanding if you used water to sand with. The water could have caused the sanding sealer to blush. If you were sanding to fill the grain it would have been better to use mineral spirits or naphtha as a lubricant.
 

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The Nut in the Cellar
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Steve, the Varathane sanding sealer is water based according to the msds sheet. I would suspect the OP logically wet sanded with water as the lubricant. I still think the haze was a result of the oil/water/sealer mix created by sanding. Regardless, using the sanding sealer over the oil based product was the source of the mess.
 

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Aniline dyes and Lacquer finishes are so much easier and simpler especially with HVLP sprayers.
You wouldn't have any of these problems and will have a superior finish. Spray on stain - wait 30 miniutes.
Spray on vinyl sealer if wanted - wait 10 minutes. Spray on 2 coats of lacquer 10 minutes between coats. Clean guns and put away - 10 minutes. Use your your project tomorrow.
 

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Discussion Starter #12
Steve, the Varathane sanding sealer is water based according to the msds sheet. I would suspect the OP logically wet sanded with water as the lubricant. I still think the haze was a result of the oil/water/sealer mix created by sanding. Regardless, using the sanding sealer over the oil based product was the source of the mess.
Yeah- I feel like an idiot. I'm usually so careful to read the instructions/data sheets, and somehow completely missed the water-based nature of the sealer. Let alone applying the sealer on top of the oil finish... that apparently wasn't as dry as I thought it was. Cascade of failures... but thanks to all you guys for all the comments- definitely help for future learning !!
 

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Yeah- I feel like an idiot. I'm usually so careful to read the instructions/data sheets, and somehow completely missed the water-based nature of the sealer. Let alone applying the sealer on top of the oil finish... that apparently wasn't as dry as I thought it was. Cascade of failures... but thanks to all you guys for all the comments- definitely help for future learning !!
Yeah- I feel like an idiot. I'm usually so careful to read the instructions/data sheets, and somehow completely missed the water-based nature of the sealer. Let alone applying the sealer on top of the oil finish... that apparently wasn't as dry as I thought it was. Cascade of failures... but thanks to all you guys for all the comments- definitely help for future learning !!
Not sure if that was the problem but any water based finish is incompatible with linseed oil which is contained in stains and oil based finishes. It really is just not suppose to adhere well, I've never heard of it making the finish milky. Any time you put a water based finish over even an oil stain you should make a practice of waiting a week before using a waterborne finish. The linseed oil needs to cure completely.
 

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Unless sanding sealers have changed their mission or I am misunderstanding, they are not meant to be used as a grain filler. There are 'paste wood grain fillers' for that.
Years ago, a sanding sealer was a misnomer. It didn't seal the pores.Way back when, I dont know what species were involved but when you stained the wood, the grain would raise during a finish coat and have to be sanded. Sometimes it happened more than once. What the sanding sealer did was to raise the grain and seal it so you could sand it and it wouldnt raise again.
I have never had a grain raising problem and so I never used the stuff.

Varathane's opening statement "..............seals wood pores and provides a surface that can be easily sanded"
Seals wood pores? What does that mean? Does it fill the wood pores? If so, why not say so? I dunno.
 
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