Please forgive the slowness of this message, as I needed to do a bit of
research since I have never actually used shellac.  I am going to make
some broad generalizations; for the non-chemists among us, they should
help explain some of what has been talked about here.  I know this gets
long.  I suggest listening to good music while you read!

The rules that cover hazardous materials are a broad set which includes
shipping regulations, environmental regulations, and human health and
safety regulations.  In the case of ethanol, the added regulations
stemming from liquor taxes come into play.  I want to discuss the
chemistry, not the politics involved in these regulations.  Federal and
state governments have their own sets of rules, so I will occasionally
mention one or the other.  I am trying to explain parts of the problem,
but I am _not_ writing a manual on the regulations!

There is also a consumer-based movement to get product manufacturers
or stores to eliminate particular chemicals from products they sell.
This seems to be mostly occurring in the food and home cleaning
industries, but it is affecting many sectors of the economy.

Shellac is a mixture of natural polymers.  As the size of the polymer
molecules varies, the solubility of them will vary as well.  The
description I read says shellac is actually filtered to remove assorted
plant and bug bits.  That process will also remove any un-dissolved
polymers (probably of higher molecular weight, and longer).

Depending on how long the raw material is allowed to dissolve, what
temperature it is, and which alcohol they use, the _exact_ mixture in
any batch of shellac that can -- and likely will -- vary.

Then there is the issue of what the lac bugs were actually eating, as
the plant variety has an impact as well.  Even in tightly controlled
reactors in manufacturing plants or laboratories, batches of polymers
almost never have one molecular weight for every molecule.  Properties
for polymers are reported as a range or an average.

Many common materials are defined this way.  The common bell curve is
one way of visualizing such a range, and a sharper or broader curve can
both indicate the same _average_ molecular weight.  However, the exact
molecular weights of the individual molecules in the two mixtures would
be very different.  That is one of the differences between kerosene lamp
oil (narrower curve of molecular weights) and diesel engine fuel (wider
curve).

So, now you have to try to dissolve this mixture.  For the purposes of
finishing wood, you want a solvent that dries fast enough but not _too_
fast.  The lower molecular weight portion will be easier to dissolve
than the higher molecular weight portion.  You could just filter out the
higher molecular weight part that stays solid, but that higher molecular
weight part will be the toughest part of the finish.  It's not an easy
problem, and, very often, you have to make hard choices.

Trust me, it's the same in a lab!  The old mantra, "like dissolves
like," is still true.  For shellac, which is a polar molecule, polar
solvents are needed.  There are many polar organic solvents but most of
them are not available to home users.

Alcohols go from the smallest molecule, which is methanol, up to
ethanol, then propanol or isopropanol, and way up from there.  The
larger alcohols will be more likely to dissolve the larger polymers,
but they also have higher boiling points and correspondingly slower
evaporation rates.

The other readily available polar solvents are acetone and MEK (methyl
ethyl ketone, also known as 2-butanone), which is an even better solvent
for things like paint in my experience.  (Again, it's a slightly bigger
molecule so it has a slightly higher boiling point).  MEK doesn't
evaporate even half as quickly as acetone, which can be very helpful.
However, MEK has gotten harder to find near me, so it may be harder to
find near you as well.

 - - -

/1/ Solvent Name
/2/ Formula
/3/ molecular weight, g
/4/ boiling point, deg. C, for the _pure_ compound

/1/           /2/      /3/   /4/
methanol      CH3OH    32    65
ethanol       C2H5OH   46    78
denatured alcohol is ethanol plus an ingredient that is _not_ edible;
  the formula is variable.
isopropanol   C3H7OH   60    82
acetone       C3H6O    58    56
MEK           C4H8O    72    80

Notes: molecular weights and boiling points have been rounded.  Stable
mixtures of alcohol with water (called azeotropes) are made which boil
at temperatures different from those listed here.  They tend to be in
the range of 90-97% alcohol and around 94-98 deg. C for boiling point.

 - - -

I have been a chemist for more than 30 years, and have worked in several
industrial labs in California for the last 20 years or so.  I have seen
many changes in safety regulations in that time and most of them are
reasonable and necessary.  However, some of them do leave even trained
chemists wondering what the rule makers were thinking!  It isn't just
California, although things like California's "Proposition 65" warning
I just saw on a paper kit I bought make no sense at all.

(California requires all products that contain chemicals that might
cause cancer or reproductive harm to have a "Proposition 65" label.
Recently, they did decide to _not_ put that label on all coffee.
I wish I was joking...  The thing is, if people see that label
everywhere they'll start ignoring it.)

Some of the chlorinated solvents that used to be widely used are
very toxic, and even chemists are very careful when using them.
(Dichloromethane, otherwise known as methylene chloride, is one
example.)  The EPA is in the process of banning that from products
for consumer use.

I like to tell people I am careful because I want to be an even older
chemist!  In the lab, I have a proper fume hood to protect me.  When
I am painting or using lead solder for stained glass at home, my
protective equipment is much less formal.

So, products go out of production or availability and you still need
them.  Reverse engineering can help.  The first step is to find the
SDS/MSDS (Material Safety Data Sheet) for the product you like.
Google makes this easy, as do the laws that any "hazardous" material
must have one, and the habit of shipping companies to require one
regardless.  (Elmer's school glue has one.)

For safety, the SDS sheets give some indication of the components of
a product.  Fair warning here: they can be very vague to protect trade
secrets, and they usually only give ranges for things like solvents
(for example, 10% to 15% acetone, 85% to 90% MEK).  But if there is
something particularly hazardous, like toluene or benzene or lead or
whatever, it will be listed by name.

Those SDS's are also how companies tell people what safety measures to
take with a product.  They can be a bit of overkill sometimes (purified
water in a tiny bottle coming with a warning that says "risk of drowning
in large quantities"), but they do give you an idea of what the science
and the company's lawyers say proper safety precautions are.  In this
case, the SDS should tell you what the components of your favored
product were, especially since some hardware store solvents give no
info.  Do also read the safety precautions -- knowledge is power!

If it were my project to dissolve the shellac, having the SDS and a list
of components to start from, I would see what of those I could get my
hands on.  Isopropanol from the drug store, ethanol from the liquor
store (the highest proof ethanol you can get in California is apparently
120 or so), methanol from the model airplane or automotive stores,
acetone and MEK from the hardware store.

There used to be a science/special effects store here in Los Angeles
that had lots of chemicals for sale, but they closed when (federal)
shipping regulations increased some years ago.  Perhaps there is one
near you?

The web has lots of suppliers that will sell to individuals, though the
big chemical supply houses will not.  I've never checked exactly what
is in the "perfumer's alcohol" that perfumery sites sell for making
perfumes, but that is another option.

Then, I would do a series of tests (both for dissolution and proper wood
coating) with both pure solvents and mixtures.  I might not find the
perfect replacement, but one that was good enough should be achievable.

If a component was not available to me, I would get as close as I could.
Not being chemically trained would make this harder, but Wikipedia and
Google should show you structures of the molecules and then you can try
to use that to get close.  I am also willing to answer specific chemical
questions to try and help.

And now, back to the music -- I'm looking forward, in the next week or
so, to putting my Gnawvolty Halloween roll in the nickelodeon!

Monica Jones
Los Angeles