Isopropyl Alcohol 100% or Denatured Alcohol for Shellac?

[ian]

Are you sure it’s metho?
We used metho to do a final clean on brake hydraulic components because it DOES NOT leave a film.

ah, the confusion between
pure methanol -- CH₃-OH
methyolated spirits -- CH₃-CH₂-OH , plus up to 50% water and an additive to make the mixture non-drinkable
and drinkable ethanol -- CH₃−CH₂−OH (a.k.a. grain spirit)
continues


so which type of "metho" are Lappa and Slave refering to ??


BTW
methanol (single carbon atom, plus an -OH), ethanol (two carbon atoms, plus an -OH), propanol (three carbon atoms, plus an -OH) are all miscible in water.
Miscible means 100% soluble.
Butanol (four carbon atoms, plus an -OH) is the first of the alcohols considered non-miscible.

[BobL]

There's a good reason most meths is typically 95% (by meths I do mean ethanol

Again from Wikipedia

Fractional distillation at atmospheric pressure can concentrate ethanol to 95.6% by weight (89.5 mole%). This mixture is an azeotrope with a boiling point of 78.1 °C (172.6 °F), and cannot be further purified by distillation.

Addition of an entraining agent, such as benzene, cyclohexane, or heptane, allows a new ternary azeotrope comprising the ethanol, water, and the entraining agent to be formed. This lower-boiling ternary azeotrope is removed preferentially, leading to water-free ethanol.At pressures less than atmospheric pressure, the composition of the ethanol-water azeotrope shifts to more ethanol-rich mixtures, and at pressures less than 70 torr(9.333 kPa), there is no azeotrope, and it is possible to distill absolute ethanol from an ethanol-water mixture. While vacuum distillation of ethanol is not presently economical, pressure-swing distillation is a topic of current research. In this technique, a reduced-pressure distillation first yields an ethanol-water mixture of more than 95.6% ethanol. Then, fractional distillation of this mixture at atmospheric pressure distills off the 95.6% azeotrope, leaving anhydrous ethanol at the bottom

In other words to produce more than 95.6% Meths costs $$

IPA is even worse as purifying IPA by simple distillation only leads to 88% IPA.

You can always make your own real methanol by heating wood chips in a sealed container and condensing the output vapour - it will contain a heap of water (and other crap) so will need secondary distillation. Because Methanol has a significantly lower boiling than ethanol it can be better separated from water,
WATCH OUT for fires.

[Mobyturns]

Bob, so when a manufacturer says their product contains "Min 99% Ethanol" they are probably telling a Furphy!

[Lappa]

ah, the confusion between
pure methanol -- CH₃-OH
methyolated spirits -- CH₃-CH₂-OH , plus up to 50% water and an additive to make the mixture non-drinkable
and drinkable ethanol -- CH₃−CH₂−OH (a.k.a. grain spirit)
continues


so which type of "metho" are Lappa and Slave refering to ??


BTW
methanol (single carbon atom, plus an -OH), ethanol (two carbon atoms, plus an -OH), propanol (three carbon atoms, plus an -OH) are all miscible in water.
Miscible means 100% soluble.
Butanol (four carbon atoms, plus an -OH) is the first of the alcohols considered non-miscible.

No confusion in my mind.
I’m talking about the common, everyday “metho” that you buy at Bunnies, Coles, Woolworths, Hardware stores labelled as Methylated Spirits.

F2D26ACB-643F-4A4D-AF2F-C0D6E07ABB75.jpeg

BTW - never heard of Methyolated Spirits - must be a Canadian thing
Also, which of the above would leave an oily film on glass?

[ian]

never heard of Methyolated Spirits - must be a Canadian thing

I don't believe that I ever claimed to be able to spel

which of the above would leave an oily film on glass?

I really don't know, but suspect that once the ethanol percentage drops below 100 proof (i.e. the water content exceeds 50%) the water might lead to observed streaking (I'm not sure that I've correctly spelled "streaking")
BobL may have a better handle on the issue.

[jack620]

Bob, so when a manufacturer says their product contains "Min 99% Ethanol" they are probably telling a Furphy!

Unlikely. They'd be opening themselves up for prosecution.

I rang the supplier in the link I posted above. They have used the wrong photo. He confirmed his IMS-100 is 100% ethanol.

So, if anyone wants 100% ethanol at a reasonable price it is available in Melbourne and Sydney from the links above. If you want to make your own poisonous methanol from wood, well you could do that too I guess.

[Lappa]

Just noted an interesting spec. on the picture I posted.

I normally buy Coles Brand Methylated Spirits which states >95% ethanol. Due to a run on Methylated Spirits (by people making their own hand sanitiser), Coles have had no stock for months.
It only came back in to my local store about 3 weeks ago and now it’s Glendale brand which I see states <95% ethanol.
Thank goodness for this thread as I was just about to make a new batch of shellac and I never use Metho with less than 95% ethanol and the Coles brand has always been successful. BTW, I always open a brand new bottle when dissolving the flakes or buttons and use the remainder for cleanup etc.

[BobL]

Bob, so when a manufacturer says their product contains "Min 99% Ethanol" they are probably telling a Furphy!

No - it probably just means they have paid to have it purified.
Like bottled water the cost of the ethanol in a bottle of ethanol is the minor component.
Ethanol costs very little to make - it's the packaging, storage, distribution and marketing/advertising that costs.


But claiming 100% purity for anything is a complete crock.
That's one thing I heavily trained in and practiced at work ie the the nominal level of impurities in any material..

And don't forget that water is not the only contaminant.
The highest purity lab grade ethanol I have seen from a specialist lab supplier was >99.8% pure and that was about $200/L
At work we further purified this by a process know as evaporative distillation - not to get the water out (in fact this process added water as we didn't care about the water) but to reduce the trace metal contaminants which were in the sub microgram per gram range. we used to lose about half the ethanol in the process

We also used to produce some of the cleanest lead free water on earth.
Starting with tap water, sediment and charcoal filters, reverse osmosis, double deionisation, triple sub boiling distillation.
At this point the lead concentration was around 10 femtograms per gram.
That's 6 orders of magnitude less that micrograms per gram (micro, nano, pico, femto)
Yet we did not claim 100%

[BobL]

I don't believe that I ever claimed to be able to spel
I really don't know, but suspect that once the ethanol percentage drops below 100 proof (i.e. the water content exceeds 50%) the water might lead to observed streaking (I'm not sure that I've correctly spelled "streaking")
BobL may have a better handle on the issue.

Not sure- there are lots of other organic materials in unpurified ethanol which are also likely to produce the streaks.

[RossM]

No - it probably just means they have paid to have it purified.
Like bottled water the cost of the ethanol in a bottle of ethanol is the minor component.
Ethanol costs very little to make - it's the packaging, storage, distribution and marketing/advertising that costs.


But claiming 100% purity for anything is a complete crock.
That's one thing I heavily trained in and practiced at work ie the the nominal level of impurities in any material..

And don't forget that water is not the only contaminant.
The highest purity lab grade ethanol I have seen from a specialist lab supplier was >99.8% pure and that was about $200/L
At work we further purified this by a process know as evaporative distillation - not to get the water out (in fact this process added water as we didn't care about the water) but to reduce the trace metal contaminants which were in the sub microgram per gram range. we used to lose about half the ethanol in the process

We also used to produce some of the cleanest lead free water on earth.
Starting with tap water, sediment and charcoal filters, reverse osmosis, double deionisation, triple sub boiling distillation.
At this point the lead concentration was around 10 femtograms per gram.
That's 6 orders of magnitude less that micrograms per gram (micro, nano, pico, femto)
Yet we did not claim 100%

I suspect they can get away with saying that because it would be considered +/- 1% (Well - minus really , given the claim) The number of significant digits in the claimed measurement impacts precision of the claim.
They probably won't get away with 100.0%

[RossM]

Methanol should not be considered for use with shellac. It causes the shellac to become very brittle and crazed.

The confusion some have is the term "methylated spirits". Be confused no more. "Spirits" is an old term for highly distilled grain alcohol, in other words ethanol. The longer term is "rectified spirits". The process of "methylating" it involved adding a small quantity methyl alcohol to poison it so it would not be consumed. The authorities wanted to ensure anyone consuming alcohol paid taxes, and the seppos did not want anyone to drink alcohol. Another term is denatured alcohol. These days we add bittering agents, rather than adding methanol to poison it, and sometimes an agent to induce vomiting.

You can substitute 2-propynol for ethanol when mixing shellac. It will marginally affect drying time, but otherwise works well.

[BobL]

I suspect they can get away with saying that because it would be considered +/- 1% (Well - minus really , given the claim) The number of significant digits in the claimed measurement impacts precision of the claim.
They probably won't get away with 100.0%

Technically speaking, to claim the default +/- 1% they would need to state it as "100. %"
Implied +/- 1 only applies to rightmost non-zero digit on the left hand side of a number with no decimal point.
Technically 100 (no decimal point) is considered as +/-100.
So 110 implies +/-10, 101 +/-1
This does not apply to digits on the RHS of a decimal point, ie 100.0 does imply +/- 0.1

This is about as nerdy as this gets because nobody actually writes 100. +/-1
We had a few debates about such minutiae on that International Science panel I served on for a couple of decades.

[Chesand]

"Spirits" is an old term for highly distilled grain alcohol, in other words ethanol. The longer term is "rectified spirits".

When some Latin terms were still used in pharmacy it was known as SVR - Spirit Vini Rect - Rectified Spirit of Wine. Showing my age now.

[RossM]

Technically speaking, to claim the default +/- 1% they would need to state it as "100. %"
Implied +/- 1 only applies to rightmost non-zero digit on the left hand side of a number with no decimal point.
Technically 100 (no decimal point) is considered as +/-100.
So 110 implies +/-10, 101 +/-1
This does not apply to digits on the RHS of a decimal point, ie 100.0 does imply +/- 0.1

This is about as nerdy as this gets because nobody actually writes 100. +/-1
We had a few debates about such minutiae on that International Science panel I served on for a couple of decades.

Now getting off topic, but - the treatment of trailing zeros in whole numbers varies and does not always follow the convention noted above, and is a real can of worms. For complete disambiguation where it matters, these numbers should really be written in scientific notation, where the number of significant digits is completely defined. Eg 1 x 10 to power 2 vs 1.00 x 10 to power 2 (the first being 100 with one significant digit and the second having three significant digits.)

However for the 100% ethanol above, there is wiggle room for the claim made; much more so if you interpret the number as having only one significant digit.