How to "thin" shellac?

October 28, 2009

More on denatured alcohol (methylated spirits) at Wikipedia. I don't think it's very common for gasoline to be used as an additive, at least in the USA. Unfortunately, the denaturants used aren't usually listed on the container, so to be safe one must assume the presence of some solvents of greater toxicity than ethanol and methanol.

October 28, 2009

More on denatured alcohol (methylated spirits) at Wikipedia. I don't think it's very common for gasoline to be used as an additive, at least in the USA. Unfortunately, the denaturants used aren't usually listed on the container, so to be safe one must assume the presence of some solvents of greater toxicity than ethanol and methanol.

David :

While I'm not a pen repair wizard, I am a chemical engineer and applied chemist, and I'd venture to say that the reason "gasoline" is mentioned as an additive/contaminant in denatured ethanol is that one of the previously used azeotropes involved benzene, which, again previously, was a substantial constituent of gasoline. The discussions of why and how benzene has been phased out from uses in many mixtures is a longish one, so I won't burden folks here with that.

Other denaturing materials like methanol and isopropanol have been mentioned, but there have also been denatured ethanol mixes with materials like methyl ethyl ketone (MEK) used as agents in the mixtures. For the most part, these agents will vapourise quite well along with the ethanol in the shellac solution, and shouldn't create major issues.

Bottom line for me is to consider that fine woodworkers have been working with shellacs for a very long time, and typically use high quality alcohols as solvents. "Cloudy shellac" is a well known problem in the business, often because of water contamination of the solution, but sometimes because of other impurities in cheaply priced alcohol supplies.

Does the alcohol need to be pure to a level with less than, say, 1 Part Per Million (PPM) of contaminants ? No, not really, because pen repair people and woodworkers aren't trying to run complex chemical reactions where catalyst poisons or side reactions are a concern. That's more the issue with some of the kinds of things that I look at in my work. OTOH, using an alcohol with several or more percent of water contamination is likely "non-ideal" with respect to the shellac drying and curing in place in a pen's internals.

Thinking about this from a cost perspective, even if someone buys higher end denatured ethanol at $20 a quart measure, that's one heckuva lot of shellac solution for pen repairs. Looking at this from the perspective of a pen repair shop, that's not an incredible overhead cost. The person making repairs to a few pens can buy a pint or half-pint and not break the bank, but in all of those cases, the users would get superior quality shellac solutions for their repairs.

Of course, all of that assumes that the shellac being dissolved in the ethanol is high quality, but that's an entirely different discussion... <arched eyebrow>

John P.

October 28, 2009

David :

Oh, and on the subjects of personnel exposure to the solvents, it's not so much the exposure to the solvents that's the significant hazard, but the potential for a flash fire and/or explosion, especially with a larger solvent spill. In "another life", as the expression goes, I investigated these things for a living, and solvent spills are a definite issue. Solvent spill cleanup should be rapid, and any rags or absorbants used should be removed from the building to outside lickedy-split quickly. There's a strong and good reason to have a small (but adequate) fire extinguisher handy in a shop to knock-out flash fires.

In general, handling these solvents should always be done with appropriate care, and with reasonable ventilation. If someone's going to be doing solvent handling full-time - something that would seem a bit odd for a pen repair person - there are indeed some industrial hygiene issues to address to limit potential exposures. That's a much more complex discussion, and is dependent on the solvents, the space where these are used, ventilation, and ultimately, specific IH testing for possible exposures. In the vast majority of cases, using the shellac sparingly on relatively infrequent occasions (i.e., not five times an hour all day) in a reasonably ventilated space should prove adequate.

John P.

Edited October 28, 2009 by PJohnP

October 28, 2009

Rubbing alcohol is isopropyl alcohol....

Not necessarily; it can be ethyl alcohol.

--Daniel

October 28, 2009

I thought all this denatured stuff was familiar. Post #11.

Solvent Todd

October 28, 2009

I thought all this denatured stuff was familiar. Post #11.

Solvent Todd

Heh. Well, the technology's not exactly new on this topic, eh ?

"Refining John"

October 28, 2009

I thought all this denatured stuff was familiar. Post #11.

Solvent Todd

Heh. Well, the technology's not exactly new on this topic, eh ?

"Refining John"

I see you are a ChemE. Me too. Got myself one of them Chemistry degrees as well. Did a short stint at a refinery in the fine state of OK. Also done some consulting work at Chevron in Richmond (CA). My favorite is still the cat-cracker with they hydro-reformer a close second. Any refining favorites there?

All sorts of fun chemistry stuff goes on in the potions we use for pens. Some fact, some fiction, and some unclassifiable. I like the unclassifiable best.

I just shot my bottle of rubbing alcohol on the GCMS. No calibrations but ~65% isopropanol and the balance water. There is a peak that I'm guessing is n-propanol that may be 0.5% at most. I'm guessing because I was to lazy to run a standard but it has the same mass so what else could it be right? I was also to lazy to go get any denatured ethanol but the 200 proof stuff is pretty clean-I'd need the KF-titrator to see the water content.

T

October 28, 2009

I see you are a ChemE. Me too. Got myself one of them Chemistry degrees as well. Did a short stint at a refinery in the fine state of OK. Also done some consulting work at Chevron in Richmond (CA). My favorite is still the cat-cracker with they hydro-reformer a close second. Any refining favorites there?

All sorts of fun chemistry stuff goes on in the potions we use for pens. Some fact, some fiction, and some unclassifiable. I like the unclassifiable best.

I just shot my bottle of rubbing alcohol on the GCMS. No calibrations but ~65% isopropanol and the balance water. There is a peak that I'm guessing is n-propanol that may be 0.5% at most. I'm guessing because I was to lazy to run a standard but it has the same mass so what else could it be right? I was also to lazy to go get any denatured ethanol but the 200 proof stuff is pretty clean-I'd need the KF-titrator to see the water content.

T :

Chuckle. I don't have a GCMS (Gas Chromatograph - Mass Spectrometer for non-chem types reading this) here, but that sounds about right. Getting IPA down to lower than mid-thousand-PPM levels of n-propanol or other C1/C2/C3/C4 alcohols just isn't worth it for a commercial bulk product. Years back, I did some contracting for an ultra-pure solvent facility where a 1 PPM contamination level would be considered unsalable, but boy howdy, they weren't selling that stuff at commodity rates !!!

I know the location you mention well - lived over in Marin County many years back, and visited most of the chemical and refining facilities in the area at different times. Haven't done much around there recently, maybe three or five years back. Pretty area. I've seen a fair bit of Oklahoma, too.

As for refining "favorites", wow, that's a hard one. HF alkylation units, delayed cokers, hydrocrackers, all fun units to work around and assess <arched eyebrow>. I worked on a polymer facility with 25,000 - 35,000 psig reactors a while back that had some interesting facets to it. Over the years, between chemical plants and refineries, I've seen a fair number of units with, let's just say, "odd aspects".

Yup, the ink discussions are fascinating when folks start to go down various roads in their discussions. I posted a thread sometime back commenting on the various theories of pen materials and ink effects, but I think I pitched it in the wrong way for folks to follow some of the discussion. As you say, there's a lot of "unclassifiable" aspects to ink chemistry. <wry smile>

John P.

October 30, 2009

Hi guys. Gerry here. As an Electrical, I s'pose I don't have the credentials to speak authoritatively in this thread, but I note that in Canada, the most popular thinner for Shellac is simple Methyl Hydrate (Wood Alcohol), which is a denatured product. It's relatively inexpensive, and pure enough for the purpose.

The paint or hardware store is the appropriate source.

Last time I bought it, prices like those quoted earlier were appropriate for a gallon container - enough to thin all the shellac you will ever buy - and fill all your alcohol burners and food service heaters etc. etc. as well. It can also be used to de-ice car door locks and is valuable as an additive to the gas tank to control water content in the winter - don't forget that it can be diluted with water to make windshield washer solution... Takes off labels well too!

While woodworkers can often be as anal as pen fanciers, (apologies to the woodworkers in the group) ;-). I don't really think we are all that concerned about cloudiness, or practically any other finish fault one might encounter - what we really need is 'sticky'. And shellac - whether it is made with flakes containing myriad impurities, and thinned with simple Methyl Hydrate (Shellac Thinner) and only 99.9% pure, is 'sticky'.

In my hobby application I have three grades of shellac. Thin, thicker (normal), and thickest. These are chosen based on a careful analysis of the application, environment and future repair needs.

If wicking is necessary, thin is appropriate. If some gap filling capability is required, thickest is the baby to go for. For all the rest, normal is just right. Others - Guru's such as Ron and / or Richard may have more finely calibrated systems, but for the great majority of us, something as simple as my system - or even one consisting of a single concentration of shellac, may serve perfectly fine. I would recommend the Normal solution in that case.

Next time I'm in Harbour Freight I'll check in to see if they are carrying any GCMS equipment (I didn't see any last time I looked) to perhaps fine tune my mixtures, but I don't ever expect to go for the KF-titrators just to see the water content. There's limits to my curiosity, as well as to my finances. <grin>

Thanks for the education though guys...

Regards,

Gerry