Hacker News Reader

Comment by dvh | Hacker News Reader

I've recently had my first experience with shellac. Bought 10g of red flakes for ~$2, dissolved it in alcohol, applied 10 layers or so. Despite being red it has some yellowness to it, smells absolutely delicious, it's relatively easy to scratch with nail (although this might be because I used pine). Dries in about day. Very glossy. I don't think it's good for things that are handled manually like a guitar. Eventually I decided not to use it and went for EN 71.3 paint/stain that is specifically designed for toys.

View on HN

When blending shellac, especially if you are using a dark color like you'd use on skirting boards then always ensure that you use 99% ethanol. Obviously it depends where you live so availability may be a problem as that strength may not be permissible. Often consumer-grade industrial ethanol is only available at 95% strength the remaining 5% water and denaturant.

The 5% water doesn't seem much but it can cause the shellac to go slightly milky in color. This can be quite noticeable if you're trying to match colors during the touch up of some old work. The transparency of the schellac isn't the same so even when you match the color you can still notice the difference. Also, if there's too much water in the alcohol then the shellac won't harden properly - or you'll notice a textural difference in the finished surface.

How long after you applied it did it scratch? Like a lot of finishes, shellac dries pretty quickly, but takes a while to fully cure.

Also: not applicable to your situation, but the lighter (in color) grades of shellac are processed in a way that means that non-fresh shellac sometimes doesn't dissolve or harden properly.

I noticed this on a closet section I just built. A day or two after finishing it would still scratch but now that it's been a while and it's in the closet being used it doesn't seem to scratch.

What alcohol did you use? The instructions I find talk about denaturated alcohol which, at least here in Portugal, has a blue tint (smells like alcohol but is poisonous).

I have used normal denatured alcohol but it does not have a blue color where I am from. It did smell bad and have adverse reaction when in contact with moisture, but it was the cheapest stove fuel alcohol and I got good results.

Specialty stores for woodwork, art supply etc sell high quality denatured alcohol for use in shellac which is higher purity and smells less bad. I haven't tried that.

You can use pure ethanol, which is easy enough to distill from wine or other rotten fruit, though this is prohibited in some backwards countries for superstitious reasons. Some people prefer isopropanol, but they say you have to be sure it's not adulterated with water. You can salt water out of isopropanol, but I don't know if the resulting salt contamination is harmful to your wood finish. Other people report success with methanol, but I wouldn't want to get it on me.

> though this is prohibited in some backwards countries for superstitious reasons

It was banned in my country after a dozen people died and more went blind after someone made a bad batch of something. Not superstition.

Methanol poisoning from distilling is superstition. Any sugar-based mash (whether it be a fruit wine, a grain beer, or a good ol' sugar mash) will produce completely negligible quantities of methanol, even if you are drinking the foreshots directly.

Methanol only occurs in home distilling if you are trying to recreate certain heavy-cellulose mashes (I've heard there's some Italian one that uses a particular wood, for example) or, more commonly, if someone is trying to de-denature alcohol, which was common during the Prohibition, which lead to the belief that moonshine was apt to blind you.

The blinding happens when drinking some common type of denatured alcohol and the only reason for denatured alcohol to exist is exactly that superstition.

> the only reason for denatured alcohol to exist

is to make sure alcoholics don't drink untaxed booze.

Pease be specific and explain exactly what you mean.

Fact 1: If you drink alcohol that has been denatured with an essentially nontoxic bitterant such as Bitrex/denatonium then with sufficient quanties you'll suffer ethanol/acetaldehyde poisoning and in the long term you'll likely liver cirrhosis - but you won't likely go blind.

Fact 2: If you drink ethanol denatured with methanol (and likely pyridine that usually accompanies it) then you'll likely go blind - and if you drink enough of it for long enough then you will definitely go blind. No ifs or buts, just scientific fact - that's if the methanol doesn't first kill you outright. https://en.m.wikipedia.org/wiki/Methanol_toxicity

Fact 3: Ethanol denatured with nontoxic bitterants (denatonium) is considered to have a better public health outcome as alcoholics will still suffer the short and long term effects of ethanol whether they drink whiskey or industrial ethanol but those negative outcomes, whilst bad, are not as bad as combined ethanol/methanol/pyridine mixtures.

Well, of course drinking the stuff is dangerous and stupid; the humans have had safer ways to disinfect water for over a century now. But the reasons it's prohibited in various places have to do with various supernatural beliefs, not sensible safety and health precautions for toxic volatile organic solvents. Obviously if you go around drinking organic solvents like an idiot you can die, but ethanol is one of the least dangerous solvents from that perspective.

Don't even think about it. It's possible that some solutions/mixtures might use methanol instead of the more usual ethanol.

Consumption of as little as 30/40ml will blind you and if you double that then it's curtains.

Methanol can cause cumulative damage and unlike ethanol it absorbes easily though the skin.

The reason I mention methanol is that in the past when rules were more lax I've used an ethanol/methanol mixture for shellac and some jurisdictions may still allow its use. As with ethanol, methanol works perfectly as a shellac solvent, also it's often very difficult to distinguish between these solvents without a proper chemical test.

I was talking about ethanol, not methanol; it's easy to distinguish ethanol if you distilled it from rotten fruit. Consumption of 30 or 40 ml of ethanol won't blind you; the humans commonly take toxic doses of ethanol intentionally and even habitually. It's stupid and dangerous, but it's not even in the same ballpark of risk as drinking methanol, benzene, styrene, or even acetonitrile.

You missed the point, methanol/ethanol and sometimes pyridine mixtures are commonplace although less so in many jurisdictions nowadays. Not only are people tempted to drink these mixtures they in fact deliberately do for their intoxicating effects - even though they know the stuff is poisonous (even conspicuous warning labels on the bottles marked 'POISON' don't stop them). In one very hot town I know the local store kept bottles of the stuff in the refrigerator for the local 'metho' drinkers - no, this isn't an exaggeration!

Whilst many of these formulations were deliberately introduced to denature ethanol so that it could be sold without having duty added, overall they've had a serious delitarious effect in that the negative outcomes from a public health perspective were much, much worse than various governments losing a few dollars in excise duty. After about a century or more, more enlightened regimes have come to the conclusion that if nothing else it's cheaper not to poison citizens who insist in imbibing the poison and they've now swapped out the methanol, etc. for Bitrex/denatonium as a non-toxic denaturant alternative.

I don't know where you live but where I do the methanaion of ethanol was commonplace until recent years. Moreover, toxic pyridine was added to make the mixture stink and yet people still drank it. Although never having been tempted myself, even I'm happy the methanol has gone as I regularly use many litres of ethanol as a cleaning agent. Before the methanol was removed I had to use the less dangerous isopropyl alcohol (propan-2-ol) for safety which was much more expensive.

The fact that methanol/ethanol mixtures were (and are) so commonplace and the fact that they've been around for so long - and that trade between jurisdictions with different poison standards is common - we cannot assume any nonfood ethanol (or ethanol as solvent, i.e.: in shellac) is pure or that the only 'additive' is water unless marked BP/pharmaceutical/lab grade, etc. Essentially, the longstanding practice of mixing these two alcohols for industrial use hasn't entirely been forgotten and that habit/old practice lingers. We've seen evidence of this recently when temporary ethanol shortages led to unscrupulous suppliers substituting methanol in hand sanitizers and the CDC having to take action.

“smells delicious” is hilarious to me. What’s the smell like?

I'm curious too. When I use shellac, it smells like alcohol.

I must be odd but I like the smell of certain organic solvents - alcohol included. Perhaps shellac adds some extra depth to the already sweet smell of alcohol and produces something that OP finds nice?

Note that I drink very rarely so this is not coming from being a heavy drinker.

yes shellac has a noticeable odor which is not entirely the alcohol. I enjoy petroleum solvents, mainly.

I use shellac, an application is dry in about 20-30min.

> smells absolutely delicious

Apart from smelling nice, is it something that is actually okay to breathe in?

https://en.wikipedia.org/wiki/Resinous_glaze

Shellac is not particularly harmful.

I thought guitars typically get a French polish which does use shellac.

Some guitars do but it's not common. Nitrocellulose lacquer was common in the 20th century and linseed oil with natural resins before that.

When I hear "nitrocellulose" I quickly get doubts if I'd want to coat my instrument in it. (If it's common I presume it must be safe, more or less, but it sure doesn't inspire much confidence in me.)

No, it is not safe, and that is why it is regulated and hard to get in many parts of the world.

Afaik the final product is pretty safe but handling the chemicals while working with it needs precautions.

Well, handling the lacquer while (re)coating a guitar would only have the typical solvent issues.

This is low-nitrated material, and the only issue there is thermal runaway that you don't have when applied as a guitar lacquer.

That nitrocellulose form is only really a problem in bulk form, like back when it was used for movie projection film.

Flakes of the lacquer just burn fast and may continue burning without additional oxygen, but the thin film inhibits any detonation waves across the surface, while the liquid lacquer form inhibits such by dilution in a solvent.

Reply on news.ycombinator.com