sick glass

[maineahh62]

hello everyone, since i respect harry's responce's and value his knowlage i have removed this info, thank you for setting me straight harry.

 

[Harry Pristis]

Hey, Tim . . .

This article is confused about "sick" glass. It does not make a distinction between calcium deposits and the leaching of soda from the glass.

If calcium deposits were our problem, tub and tile cleaners would be our salvation. Even straight vinegar (why bother to mix it with water?) would suffice. Calcium deposits are easily removed -- this is not what I would call "sick" glass.

The cloudiness that develops on glass put through the dishwasher is real chemical etching, like that which develops on a lot of buried bottles.

Ammonia and hydrochloric acid do not affect glass, as far as I know; but, HCl is certainly "overkill" for calcium deposits.

My opinion is that this article will confuse newbies.

----------Harry Pristis

 

[Dirranbandi]

Hi

The article could confuse new collectors as it seems more applicable to glassware that has not been in the ground, rather than bottles which are buried and come in contact with mineral deposits, etc. that impact on the glass. Over here in Australia a lot of bottles come out very cloudy/soda-ery in appearance due to mineral content leaching into the glass- soap/water or vinegar/baking soda tend to have only surface/superficial effect as it is in the glass - for the rare items, most collectors tend to polish.

Des.

 

[Tandy]

[]

Greetings to all from South Australia!

I read with interest the posts on "sick glass", especially that from Dirrabandi.

Here in Soutrh Australia we have decidedly alkaline soils, with the result that may of the bottles we dig up tend to be "sick" to a greater or lesser degree, and when describing the condition of these bottles, the term "dug condition" is often used. I believe that the thin film deposit known as "sick" is actually a very fine layer of silica, I know that acids have no effect on it, so it can not be a carbonate deposit.

I agree with Des that it does not really come off unless you polish the bottle.

However, if there is a choice between a slightly sick bottle or no bottle, I know the choice I would make, and have done so many times. A better quality bottle will often turn up later.

 

[Harry Pristis]

I am puzzled that you blokes continue to refer to the patination (sickness) of glass as "a deposit" and to mineral deposits "leaching into the glass." It is neither.

As long as you keep referring to decomposition as "a deposit," newbies will search for some chemical that will remove it. The white frosting and the iridescent flakes are the bottle-glass decomposing, NOT some foreign material picked up from groundwater.

Here is what Van den Bossche (a trained engineer in glass technology) says:

patination: Coloured layered crust that is produced by decompostion of the glass (weathering) and is quite distinct from the unaffected glass itself. Patination should be regarded as a natural process of decomposition of glass buried in the ground or in water.... Some bottle glass is more prone to decomposition and some environments tend to accelerate the process.

Here is what Cecil Munsey says:

The name ["sick glass"] is actually very descriptive--the glass is "sick"; it is dissolving. Glass is often thought to be highly resistant to chemical attack. Glass is, however, subject to slow corrosion by water. Over a long period of time moisture will leach out the soda and lime in glass and leave behind a silicate skeleton.

Munsey's "silicate skeleton" is a good way to think about the iridescent layer which may flake away.

-----------Harry Pristis

 

[bigkitty53]

Very interesting and informative article Harry.(As usual![]) A friend of mine has an 'onion' that he has kept in a bucket of fresh water for years now.He dove it up in the early 90's and after cleaning off the coral noticed that the bottle was literally exfoliating. (shedding fine flakes of glass,like dandruff!) He resorted to the permament freshwater bath as it seems to slow the deterioration.I will pass on your article to him Harry but I'll pre-empt what I'm sure will be his first question; "Is this condition irreversable?"
I know he had the onion on display in the open air for quite a time without any slowing of the breakdown,before resorting to the bath.

Thanks Harry!

KAT

 

[Harry Pristis]

Hello, KAT . . .

Ivor Noel Hume in his book, HISTORICAL ARCHEOLOGY, (1980) says this about your friend's problem:

Drying the decayed glass in acetone and then impregnating it with epoxy varnish in a vacuum tank has been successful in treating bottles recovered from wreck sites. But first it is necessary to wash the glass in running fresh water for a long time to remove all the salts.

It is the salt crystalizing which causes the residual silicate skeleton to exfoliate.

----------Harry Pristis

 

[bigkitty53]

Many Thanks,Harry!

KAT