bottles developing cracks after dug

[Bottleman]

Hello, I have a question here about digging bottles and having them crack on you later. I have dug some bottles in the past that look perfectly fine when I pull them out of the hole but about 10 mins later they will either develop cracks or tiny bruises will become bigger. It mostly happens with milks and crown tops sodas. I am not sure if it’s from the temperature change or what but it’s a pain in the butt! Has this ever happened to any one else out there or is it just my luck?

Thanks, Tom

 

[IRISH]

It tends to happen with bottles from around the WW1 era, it was lack of ingredients or experimentation or both that resulted in very hard brittle glass that has very little "flexibility" (not really the correct term but it's discriptive [] ), and often in glass that has a lot of Manganese Oxide in it. It is a combination of temperature change and pressure change, some tips here are well known for it as they are compressed and date around the 1915 mark.
It's a bit stressfull digging good bottles in that sort of tip but all you can really do is keep them out of sunlight and try to adjust them slowly to the temp of the day, I've dug a tip in NSW like that and we put them under a towl to try to slow the stress on the glass.

(EDIT= I must learn to spell one day [] )

 

[diggerjeff]

older bottles that are cooled to quickly tend to have a lot of internal stress in the glass. avoid quick temp. changes and hot or cold water.

 

[kastoo]

yea I heard of this before. You have to wrap them immediately when you dig them from a warm place and bring them into the cold. Some even take them to their car as well.

 

[Bottleman]

Thanks for all the information you guys have given me. I will have to try that next time I dig a good bottle.

~~Tom

 

[Leisalu]

After over 30 years of digging experience I can tell you this; Here on the West Coast some of the bottle glass that was produced in San Francisco prior to about 1885 is extremely fragile. I once watched a $10,000 green Laquor's Bitters I had just dug crack before my very eyes ! I was a warm day and within 15 minutes of that bottle coming out of the ground it stared to develop fractures and large cracks. Not un common at all to see early Western glass with annealing cracks and fractures caused from slight temperature changes. The only way to help prevent such a thing is to very slowly stabilize it. What I do now is as soon as it hits daylight it goes into a bucket of dirt from the hole which is the same temp as it came from. I'll put the bucket in my garage and let it sit there for a few days. I don't do this with everything only the killer jugs that I know are made of the early fragile Western glass. I also pack an ice chest just for the good jugs and keep it cool. Glass fractures when it gets warm because the molecules expand with warmth. Just even the difference in a few degrees can cause damage on some bottle glass especially after it comes out of the ground where in most cases it's laid for over a hundred years.