jgourlay
Just Promoted to troublemaker
Registered: 12/06/02
Posts: 9838
Loc: Houston, Texas
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I keep finding myself in the same trap. I am close to getting ready to finish a project. I order shellac flakes. Something happens that delays the finish of that project. Or the project requires 1/10 of a pound of flakes and I have a lot left over.
Sometime (years?) later I have a project and I think "oh! I've got shellac flakes!" And, like Friday, I let the shellac sit in the alchohol for 48 hours and all I get is snotty glop. I have roughly a lb of garnet ($30) and a lb of blonde ($30) both in the same shape! 
Would storing in the freezer in a solid container prolong storage of the dry flakes? How about a solid container with bloxygen squirted in? How about a solid container with bloxygen squirted in, in the freezer????
Is there any help/hope? 
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chemmy
Member
Registered: 05/12/12
Posts: 178
Loc: Knoxville TN
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jgourlay said:
I keep finding myself in the same trap. I am close to getting ready to finish a project. I order shellac flakes. Something happens that delays the finish of that project. Or the project requires 1/10 of a pound of flakes and I have a lot left over.
Sometime (years?) later I have a project and I think "oh! I've got shellac flakes!" And, like Friday, I let the shellac sit in the alchohol for 48 hours and all I get is snotty glop. I have roughly a lb of garnet ($30) and a lb of blonde ($30) both in the same shape!
Would storing in the freezer in a solid container prolong storage of the dry flakes? How about a solid container with bloxygen squirted in? How about a solid container with bloxygen squirted in, in the freezer????
Is there any help/hope?
Unfortunately, esterification [plasticizing] of liquid shellac is unstoppable unless you use anhydrous isopropyl, ethyl alcohol wont do!!
As to lac - flakes/buttons/seeds/etc. - your less refined lacs are best if you have the ability to dewax and filter for lightness of color. still, you may only get a few years out of them as to storage. Keeping the in a cool dry place will help alot but as to freezing i'm not sure - will have to research that - it's never come up and I've never done it personally.
bloxygen or other inert gases are no help, it's not a oxidizing product. If it were me and there are or were long times in between jobs for what ever reason i would just buy quarts of zinsser sealcoat as needed. Unless your using a heavier cut than 2 lbs.?
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JR1
Member
Registered: 09/09/10
Posts: 6546
Loc: Teller country, Co, USA
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While temperature and light are problems, the big one is oxygen! Double sealing bags and forcing all the air out helps but an inert gas— Argon —does much better. Argon AKA Bloxygen is readily available and helps keep finishes longer; not just shellac flakes. Its used in welding and is readily available in small cylinders as well as the really small Bloxygen container. (It also works better than Vaccuvin for preserving wine flavor).
The small industrial cylinder with a regulator runs ~$200 a refill runs about $20 and the cylinder holds around 80x as much as the $20 Bloxygen bottle foes.
Also using something like a SealaMeal® can help.
I'm only aware of one test using refrigeration that lasted more than a few months and I can't find that online. I don't know of any tests using UV exposure of flake or temperature studies. AFAIK there are no tests using seed or button. IME flake is just fine after 4+ years; but I store mine at ~60ºF in the dark in double sealed bags. I recently started using Argon and have had great results for other finishes but haven't used it long enough to say for sure how well that it works for shellac.
Quote:
bloxygen or other inert gases are no help, it's not a oxidizing product.
Unfortunately not true.
A Number of studies show that exposure to oxygen over ~3 to 7 years will make shellac flakes unusable. Including some done by FWW.
Edited by JR1 (06/24/12 05:00 PM)
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chemmy
Member
Registered: 05/12/12
Posts: 178
Loc: Knoxville TN
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Modern shellacs are already treated with anti-oxidants after processing in India before being shipped to the final processors there here or elsewhere. Keeping it under vacuum or cool and dry wont hurt, but the actions of the other materials used in it's processing still remain the real culprits. the problem with keeping it long term is due to the materials used in the processing, Sodium hypochlorite used to bleach it attaches to the lac and has deleterious affects as well as the oxalic acid used to give the glossy look.
The best way to keep it if you must is in the least refined state as possible. I have 20 year old button lac that still dissolves just fine, though i can see when last solved it is becoming unusable in the near future. Nothing special was done to it or with it till the time i needed to solve it in alcohol, then i would dewax and filter and de-colorize as needed, without the aid of chlorine or oxalic or sodium carbonate or sulfuric acid or even anti-oxidants.
That said, if you prefer not to go that route, then i still suggest purchasing the sealcoat as needed or go to shellac.net and by it in smaller quantities if lighter than sealcoat lac is needed and you don't want to decolorize it yourself.
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chemmy
Member
Registered: 05/12/12
Posts: 178
Loc: Knoxville TN
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""Unfortunately not true.
A Number of studies show that exposure to oxygen over ~3 to 7 years will make shellac flakes unusable. Including some done by FWW.""
I'm not saying it has no affect, it's just not the main culprit. Keeping it sealed and vacuumed and cool may help, but it won't stop the other chemicals from taking thier toll on the lac. My info does not come from FWW or others it comes directly from the shellac institute in India and thier chemist.
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JR1
Member
Registered: 09/09/10
Posts: 6546
Loc: Teller country, Co, USA
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OK so maybe I'm looking at disinformation. Any references? I admit I haven't tried any tests.
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chemmy
Member
Registered: 05/12/12
Posts: 178
Loc: Knoxville TN
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Degradation of lac with storage and a simple
method to check the same
Dipendra Nath Goswami, Niranjan Prasad, Bangali Baboo,
Kaushal Kishore Kumar and Mohammad Fahim Ansari
Indian Lac Research Institute (ICAR), Ranchi, India
Abstract
Purpose – The purpose of this paper is to find out a convenient chemical treatment for seedlac and shellac (semi-refined and refined commercial forms
of natural resin lac, respectively) for preventing degradation during storage at room temperature condition.
Design/methodology/approach – Seedlac and shellac are treated with a dilute solution of an antioxidant before storage. This method has not been
attempted before. The changes in the physico-chemical properties of both untreated and treated resins are investigated periodically during storage.
Findings – Antioxidant delays the degradation of seedlac and shellac at least by six to eight months during the early period of storage. It is further
observed that oxalic acid, used in the trade during conversion of seedlac into shellac by hot filtration for imparting gloss on shellac flakes for attracting
buyers), causes rapid polymerisation of shellac resulting in zero value (100 percent decrease) of flow (fluidity) within 30 months of storage, whereas,
shellac prepared without treatment of oxalic acid could be stored beyond that period without a significant deterioration in its qualities.
Research limitations/implications – Antioxidants are known to be scavengers of OH groups. Lac resin (shellac and seedlac) contains five hydroxyl
groups and one carboxyl group. Thus, only one dilute concentration of antioxidant is used to avoid possible modification of seedlac and shellac.
Practical implications – Consumers of shellac are not aware of the ill effect of oxalic acid treatment being practiced by processors. The results
obtained in the present study will help consumers to advise processors suitably before purchase and will be able to store shellac for a longer period if it
is not treated with oxalic acid. The consumers may also use an antioxidant to delay degradation of seedlac/shellac.
Originality/value – The results obtained in this paper, regarding the effects of treatments of antioxidant and oxalic acid are not available in any
previous publication. These are reported for the first time.
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JR1
Member
Registered: 09/09/10
Posts: 6546
Loc: Teller country, Co, USA
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Thanks that's interesting. But it tends to support the idea that oxygen causes or accelerates shellac polymerization and unusability. It does point out two things:
oxalic acid—a strong bleach and moderate oxidizer is very detrimental to shellac,
and there are other chemicals in shellac that could cause problems.
Unfortunately the problems were not identified not was a mechanism given.
So the paper identifies oxidizers as a big problem by inference. But the other chemicals could be why old shellac coatings don't dissolve in DNA but just soften.
Still looks to me like oxygen is the major culprit.
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chemmy
Member
Registered: 05/12/12
Posts: 178
Loc: Knoxville TN
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There are lot's of culprits like i said earlier. the more processing it goes through and the more chemicals used the worse the problem becomes. My button lac has only recieved heat treatement and thats it. In fact even seed lac goes bad long before button does, which indicates that heating lac actually improves it longevity. That also why i believe the hand methods of making flake lac are better than the solvent methods used by most others. You want a long lasting lac? Go for the button!
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rschissler
Member
Registered: 02/24/06
Posts: 1578
Loc: San Diego, CA
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Despite all the technical talk here  ...  , "years" is a long time to expect any finish to last, no matter how it is stored.
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