What happens to the wax in shellac when it dries - Woodworking Talk - Woodworkers Forum
 
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post #1 of 11 Old 12-28-2017, 06:59 PM Thread Starter
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What happens to the wax in shellac when it dries

I've mostly used shellac as a sealer, so I've only used dewaxed. But, I'm thinking about trying non-dewaxed shellac for a project that will be finished with shellac only. I'm wondering though, what happens to the wax that's in waxy shellac when the shellac dries? Does it come to the surface? Does it make it cloudy? I'm assuming the wax doesn't impair adhesion of subsequent coats as long as they're also shellac, right?
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post #2 of 11 Old 12-28-2017, 07:08 PM
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I have no idea if more of the wax comes to the surface when it dries. The wax is just part of it and stays there. It doesn't cloud the finish nor interfere with subsequent coats of shellac. You know shellac melts into the dried coat of shellac so it doesn't go on in layers like varnish does.
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post #3 of 11 Old 12-28-2017, 07:55 PM
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I have read that the wax in shellac can cause adhesion problems with other types of top coats. Like Steve said shellac dissolves into previous layers. I've never used shellac that wasn't dewaxed. I've always filtered it prior to using it on any project.
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post #4 of 11 Old 12-30-2017, 12:52 PM Thread Starter
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I've seen articles that talk about setting the shellac aside and letting the wax settle to the bottom, then pour off the clear shellac. Does anyone know of a reason not to do that?
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post #5 of 11 Old 12-30-2017, 01:18 PM
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Quote:
Originally Posted by Quickstep View Post
I've seen articles that talk about setting the shellac aside and letting the wax settle to the bottom, then pour off the clear shellac. Does anyone know of a reason not to do that?
If you take any finish and put it into a jar and watch it over days the finish will settle to the bottom and the solvents come to the top. By pouring off the top of your shellac solution you will be getting mostly alcohol and then throw the finish away. It's why every time a finish is used it should be thoroughly stirred or agitated.

I can't tell you specifically but there is a method of filtering the wax out of shellac. This is how Sealcoat is made. You might do some homework and find out what is necessary in the forms of filters. Unless you plan to topcoat the shellac with polyurethane I don't see the need to worry about the wax. It's just a natural part of the finish and more than likely the finish would last longer with the wax than without it.
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post #6 of 11 Old 12-30-2017, 04:48 PM
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Back in the late '90s, I started de-waxing shellac by filtering it through coffee filters. I have a brew basket from an old coffee maker and use it to hold the filters while the mixed shellac passes through them. Depending on the amount of wax in the shellac, it may take multiple passes. I usually start with one filter, then go to two stacked, and finally three layers. If you start with too many layers, they will clog and not filter. This method is much faster than the old fashioned settling method and produces a clear shellac. Orange shellac will end up looking clear like tea.

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post #7 of 11 Old 10-26-2018, 01:38 PM
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Originally Posted by Steve Neul View Post
If you take any finish and put it into a jar and watch it over days the finish will settle to the bottom and the solvents come to the top. By pouring off the top of your shellac solution you will be getting mostly alcohol and then throw the finish away. It's why every time a finish is used it should be thoroughly stirred or agitated.

I can't tell you specifically but there is a method of filtering the wax out of shellac. This is how Sealcoat is made. You might do some homework and find out what is necessary in the forms of filters. Unless you plan to topcoat the shellac with polyurethane I don't see the need to worry about the wax. It's just a natural part of the finish and more than likely the finish would last longer with the wax than without it.

Not exactly. Essentially, the wax is settling because it is less solvable in the solvent. It's essentially a precipitation extraction. This is in fact how they dewax the shellac; however, instead of letting it sit, they pass it through a filter. Since the wax forms a precipitate, the wax gets caught in the filter. The rest of the resin remains dissolved and as a result, passes freely through the filter.
However, it could depend on the solvent and the temperature. If the solvent does not dissolve the rest of the resin sufficiently, one could imagine some of it settling with the wax. However, DNA and 95% ethanol both are more than sufficient at dissolving the resin. In fact, some extraction processes use a rather poor solvent, but heat the solution up to a point where the resin's solubility is sufficient, but the wax still crashes out.

If anyone is worried, just simply weigh your dewaxed shellac in a jar and add their favorite solvent. Then, after settling occurs, come back and decant the solution (supernatant), let what has settled in the bottom dry out, and then weigh again. With this, you will be able to calculate how much of your solids have been removed by this process. I doubt you will find that most of the solids will have precipitated from the supernatant. I would also wonder how much of the precipitate is just more wax that was then purified out again by a second run.
Cheers!

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post #8 of 11 Old 10-26-2018, 02:02 PM
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Do an experiment: Decant 250 ml (1 x 8 oz cup) of the shellac finish into a clear jar.

Top it and put it in your fridge, undisturbed, overnight.
I'm wondering if you will see the wax condense as visible particles ( unknown sizes).
I'm guessing also that the shellac will recover if/when it is warmed up in a hot water bath.


Most biological waxes melt at approx 60C/150F so it is well below even the boiling point of water.
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post #9 of 11 Old 10-27-2018, 12:22 AM
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Originally Posted by Robson Valley View Post
Do an experiment: Decant 250 ml (1 x 8 oz cup) of the shellac finish into a clear jar.

Top it and put it in your fridge, undisturbed, overnight.
I'm wondering if you will see the wax condense as visible particles ( unknown sizes).
I'm guessing also that the shellac will recover if/when it is warmed up in a hot water bath.


Most biological waxes melt at approx 60C/150F so it is well below even the boiling point of water.
The wax melting point is not its solubility. So what you need to measure, and what we are comparing, is the solubility of wax vs other resins of shellac in DNA at a given temperature. Typically, solubility increases at higher temperatures and decreases with lower temperature, which is why beer foams as it is warmed since CO2 is less soluble at a higher temperature.
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post #10 of 11 Old 10-27-2018, 12:48 AM
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Certainly, the melting point has little to do with solubility which will change across the selection of solvents.

My point: to reconstitute the shellac, IF the wax crystallizes out, will be to heat it. That's what I suggested doing.
The increase in molecular motion is measured as increasing temperature.

However, gases tend to dissolve much more in cold liquids than in warm liquids.

That might be what you meant with CO2 and beer.



In terms of finished appearance, I've been using MinWax Tung OIl Protective Finish for years

to see everything from satin to water-wet glossy on wood carvings. It is not entirely Tung Oil.
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post #11 of 11 Old 10-29-2018, 05:33 PM
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Originally Posted by Brian T. View Post
Certainly, the melting point has little to do with solubility which will change across the selection of solvents.

My point: to reconstitute the shellac, IF the wax crystallizes out, will be to heat it. That's what I suggested doing.
The increase in molecular motion is measured as increasing temperature.

However, gases tend to dissolve much more in cold liquids than in warm liquids.

That might be what you meant with CO2 and beer.



In terms of finished appearance, I've been using MinWax Tung OIl Protective Finish for years

to see everything from satin to water-wet glossy on wood carvings. It is not entirely Tung Oil.

Haha, yes. Thanks for catching that. Not sure what went through my brain there. Gases are more soluble at lower temperatures. One of the reasons that cooler water has more oxygen if you're in to fishing.
Cheers!
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