Thread: Ozuku JNat: problem using shellac

Originally Posted by heirkb

That's kinda what happened to mine. EDIT: it didn't really get white on mine, just a little dull. What did you do to that one stone that was coated with the old shellac?

I just left it as is, but you can sand and reapply new shellac.
It also could be possible to go new shellac on top of what you have now but I can;t be 100% positive it will work, never done it.

To add to the troubles, this stone may have su...holes under the microscope full of slurry. Hope I can send it back if that turns out to be the case

Just a thought, but not a tested solution. You might try as a noninvasive course of action to submit the shellac to fumes of the correct solvent. An upside down glass aquarium would do the trick or some other sealed container that would not absorb the gas, and in a bowl place some of the solvent and next to it set the stone with the shellac to be removed. Hopefully the offensive material would just peal off. If it was a valuable antique the person might try this on a test sample, and for that matter in your other attemps to remove the shellac, you might coat some other object and do trials on those, like a block or other common stone, just to see how it progresses. alx

Shellac is peculiar stuff, a natural wax that results from insects feeding on the sap of the Acacia tree in India and secreting a waxy shell for themselves. It's been in use for literally thousands of years and has recently been popular since the renaissance. Today it's still used in industrial applications as well as some woodworking and always on fine antiques (museum-quality "French Polish" finishes). In the past it was also used on wood floors, balustrades, trim, etc but has fallen out of use in general thanks to polyurethane (NOT imho because poly is superior but because of mass-marketing and it's easier to be skill-less and lazy- kinda like cartridges btw!). These days shellac is poorly understood.

Alcohol is the most usual solvent for it, ammonia will work. Denatured alcohol is best (strongest) but vodka or moonshine will work too. Mineral spirits, turpentine, etc have NO effect on shellac- MUST be alcohol or ammonia.

Shellac is the finest sealer known (air, moisture, other molecules won't penetrate it) and it's also edible (used to wax fruit and cholocate, make medicine capsules, etc) but denatured alcohol is poison so DO NOT EAT IT!

It's inert, non-toxic, and will penetrate your stone and hold it together better than anything I know of (dunno what the Japanese use but I suspect it's similar- old lacquer is). It also lasts darn near forever- the ancient Egyptians used it extensively and it's STILL in great shape (whereas polyurethane peels off after 30 yrs or so).

Even though the can says to wait for 1 hr between coats that doesn't mean it's fully "cured" in that time. Shellac has the peculiar property of being "reactivated" by a subsequent application of solvent, or another layer of fresh shellac containing solvent. So what happened to you is that you wound up with one big thick layer of shellac that wasn't cured and so was still soft and therefore vulnerable to pressure and your fingerprints.

Another thing about shellac is that it hates water. It'll hold up ok to water, but if that water isn't wiped off after a while it'll soften the shellac and possibly turn it white. On furniture the way to remove white marks is by rubbing in some olive oil. If that doesn't work then apply VERY lightly a touch of alcohol to re-activate the shellac and let it re-cure, which will return it to a transparent state.

Anyway, your shellac wasn't cured and during this time it absorbed moisture and turned white. It will even do this if you apply it on a rainy day, as it pulls moisture from the air. It's the waxes in shellac that turn white. You can get de-waxed shellac but I think something is lost there and it's still vulnerable to water. But just use whatever you have. Zinsser makes "clear" and "yellow" or "orange"- I forgot. I'd go with "clear" as many layers of colored will build up a lovely although possibly unwanted "antiqued" patina.

If I were sealing a hone I would dilute the stuff from the can with equal parts denatured alcohol and do 2-3 coats (10-15 mins between coats). Then I'd dilute the stuff from the can with 1/2 to 1/3 denatured alcohol for a few more coats (again 10-15 mins between coats). Then I'd do 1 or 2 or 3 coats with stuff straight from the can (20-30 mins between coats). You don't want or need it too thick. Shellac goes a long way so each round shouldn't take more than a few tablespoons. Mix it in plastic or glass containers. The traditional way is to apply it with a cotton or flannel pad (a 5"x5" or so lint-free bedsheet or t-shirt folded into a 1"x1" or so pad is what I'd use- dip it into your solution and then squeeze most of it out, leaving it moist with solution) but a decent brush will work too but will be less neat. Clean-up is with denatured alcohol.

Btw, I don't wait 1 hr between coats because alcohol evaporates nearly instantly so the shellac is workable very quickly. It won't be hard in 15 mins, but it'll take another thin coat. When done it let it cure for 24-36 hours, basically until the denatured alcohol smell is not detectable when my nose is next to it. For a whetstone I'd wait as long as possible but in less than one week it'll be ready for sure.

I've never sealed a hone with it, but I've done alot of woodwork and used it to seal stone and concrete and terracotta before. More porous material needs more shellac, less porous calls for fewer coats. The key with shellac is to apply more very thin coats, not thick at all. Hence the moistened cloth wiping application.

If I were in your shoes with a bum shellac job I'd wipe the old shellac off with copious amounts of alcohol. It'll take some time to soften and return the shellac to it's fluid state, but the more you apply and the more you rub, it'll eventually come off (15 mins?). Sandpaper might help, but shellac gums sandpaper quickly and could mar the stone and alcohol works better. Then I'd assume my stone has been penetrated with some thinned shellac, and would proceed with a few more 50/50 thinned coats, then 70/30, then maybe full-strength as mentioned above.

If the bum shellac job makes for an uneven surface, and you don't like those cosmetics, what I do is apply several coats and wait 12 hrs to sand it smooth with 600 grit, then dust it off and apply more coats. For a mirror-like finish I make quick passes with the cloth, wait 12 hrs, then smooth it out with 0000 steel wool, then dust and do some more passes. Finally, I give one light final "polish" with the steel wool and apply furniture wax 3x with the steel wool and then buff it out. If you want your stone to glow you can try it but experiment on a smooth scrap of wood.

Whenever I'm working with shellac I wear latex gloves. And work somewhere drips and mess don't matter- things can quickly degenerate into a gummy mess. Change gloves frequently. Obviously you don't want shellac on your honing surface, so be careful. If you do get some where you don't want it a diligent scrubbing with a lint-free cloth and alcohol will get it out.

Moisture dripping down the side of the hone shouldn't affect the shellac much- just dry the stone as you usually would and give it time to air out. If it is a problem then apply some carnuba car wax normally, which will give an enhanced moisture barrier. In 20 or 30 years you might want to touch up your sealing job, otherwise be confident.

Way too much information, but I love this stuff and know it well. It's old school and worth the trouble.

Wow, thanks for all that great info. I'll have to try to get this current coat of shellac off and see what I can do. The weird thing is that the current coat has actually started to look a lot better and isn't getting prints on it anymore. I'll keep it for a few more days and see if the issue was the heat/quantity of water that it was in contact with during the lapping.

Originally Posted by Rubicon

It's inert, non-toxic, and will penetrate your stone and hold it together better than anything I know of (dunno what the Japanese use but I suspect it's similar- old lacquer is). It also lasts darn near forever- the ancient Egyptians used it extensively and it's STILL in great shape (whereas polyurethane peels off after 30 yrs or so).

Nice in depth answer Rubicon

The Japanese use Urushi Toxicodendron vernicifluum - Wikipedia, the free encyclopedia

Not a very user friendly goop but safe when dry & super durable.

Originally Posted by onimaru55

Nice in depth answer Rubicon

The Japanese use Urushi Toxicodendron vernicifluum - Wikipedia, the free encyclopedia

Not a very user friendly goop but safe when dry & super durable.

Now Urushi is not used so common for hones.
The alternative urushi which is "Cashew" is used.

I use this clear type:
�‚‹@”\“h—¿ˆê——/ƒJƒVƒ…�[“h—¿/�ã“h‚蓧–¾—Þ [‘å‹´“h—¿Š”Ž®‰ïŽÐ]

It is made by Cashew Co.,Ltd. but I do not know if it is available outside of Japan.

Cashew Home Page

Originally Posted by DrNaka

Now Urushi is not used so common for hones.
The alternative urushi which is "Cashew" is used.

I use this clear type:
�‚‹@”\“h—¿ˆê——/ƒJƒVƒ…�[“h—¿/�ã“h‚蓧–¾—Þ [‘å‹´“h—¿Š”Ž®‰ïŽÐ]

It is made by Cashew Co.,Ltd. but I do not know if it is available outside of Japan.

Cashew Home Page

Not available in US.
The vendors in Japan I know sell it , can't ship to US because it has flammable solvents. Unfortunately we are stuck with regular lacquers here.

Originally Posted by heirkb

Wow, thanks for all that great info. I'll have to try to get this current coat of shellac off and see what I can do. The weird thing is that the current coat has actually started to look a lot better and isn't getting prints on it anymore. I'll keep it for a few more days and see if the issue was the heat/quantity of water that it was in contact with during the lapping.

It's looking better and holding up better now because it's cured.

Without seeing it, I'd still be thinking that what's on there is compromised. You can see how long it lasts but it might not be sealing properly and then, when some moisture seeps into your stone, it might hold more of that moisture in and for longer- the exact opposite of the purpose of sealing it.

Were I you I'd be tempted to soak a good lint-free cloth or non-shedding brush in denatured alcohol and neatly "slop" as much onto the shellac as I could, over the course of 10-15 mins or so- however long it takes to re-soften it. This will re-activate the shellac that's on there, allowing it to then cure moisture free, in a more even coating, and therefore make a newer and better and more durable seal. May as well slap a few 50/50 (equal parts can solution and denatured alcohol) while you're at it.

A quart of denatured alcohol should be a few bucks at any hardware store.

Anyway, good luck with it. It's always fun to experiment with something new!

Originally Posted by onimaru55

Nice in depth answer Rubicon

The Japanese use Urushi Toxicodendron vernicifluum - Wikipedia, the free encyclopedia

Not a very user friendly goop but safe when dry & super durable.

Thanks alot for that info. Without knowing anything about it beyond that wikipedia article, it strikes me as "rubber-ish", and as it wants to cure in a humid environment and makes a waterproof seal, it seems perfect for hones.

The cashew info is interesting as well. I wonder what other uses these materials have. I do know Cashew plants are very versatile, and the juice of the fruit is milky and sticky, but I didn't know it makes a sealer as well.

As any kind of "wet" application is the last thing I'd think of for shellac, both of these seem better materials. I personally have pushed the boundaries of shellac so I think it's useful for stones, as long as they get wiped down afterwards and aren't subject to a prolonged soaking. It has the additional benefit of being natural, inert, and long-lasting (not to mention easily available). It does give a superb seal and as more can be re-applied at any time (fusing to the old layers), maintenance is simple.

Plus, it's easy enough to remove with a good alcohol scrubbing.

Regarding availability, perhaps the raw/dried urushi/cashew material can be procured in Japan and then mixed with the proper solvent by the user. Shellac, for example, is available in flakes (which can be shipped anywhere) and then mixed by the user according to preference. If cashew and even urushi works the same way then we'd have something new to experiment with!