Plaster of Paris set in test tubes

[Ocean Breeze]

I have several dozen test tubes, with rock solid plaster of paris set in them.

I didnt get to them quick enough after the expt.
Any one got a clue how to rescue my test tubes?

I have tried... scraping, boring, warming, soaking in water, in acids and in laundry detergent.
Unfortunately, it now is set like marble.
I have used a lot of acid in them, and would rather not waste any more.
However, they a re my good new pyrex boiling tubes.
Any suggestions welcomed

[Lyn]

My first suggestion is to kiss them goodbye. Second suggestion is to soak for a very long time in the fabulous napisan of which I use the generic/cheaper brands packaged by the big supermarkets. It is the same strength of sodium percarbonate 346g/kg. I had some very plaster encrusted plastic beakers which no amount of soaking was working. Chucked a considerable quantity of the magic powder in the bucket of beakers and promptly forgot about it. Took several weeks or more and when I finally faced the clean up, the plaster seemed to have dissolved. Anyhow I have clean plastic beakers once again. If you want to retrieve your boiling tubes anything is worth a try. I hope you will advise your science staff that this particular prac should be turfed out the window or suggest using disposable plastic containers next time if they wish to persist with this practical.
Lyn.

[Ocean Breeze]

Thanks Lyn.. I am off to try this one now. May even leave then to soak till after the hols.
Usaully that prac isnt a problem, but they were left over the weekend, then I left the washing up for another few days.... palstic tubes are a great ide. That way we can 'bend' the tubes to dislodge the lump. Brilliant!

[estelle]

Hello,
Have you tried vinegar, because that is what is used to slow down the setting time of plaster of paris compared to salt to speed it up.
Estelle

[Labbie]

Talking of Plaster of paris: Where do people purchase their plaster from?????

I use to be able to buy it in BIg W, but not any more. I do know Q-stores has it. But it was so much more cheaper in Big W.

[jat]

Don't know how it compares in price but I purchase my plaster of paris from Bunnings! The Penrith Store carries it so would presumme all stores would?

John

[sunray18]

I got some Plaster of paris from Bunnings! Much cheaper than any of my suppliers .. I have also managed to find it at art supply places - but it is more expensive from them...
As to the test tubes.. if you look at how much they cost you as against the cost of cleaning them [taking into account the time you take, your wages, the cleaning solutions used] - it is not cost-effective to clean them ...
Chuck them out ....
You will feel so FREE

[Ocean Breeze]

Good one mushroom! I lke the 'free' ! Thats what I need, more "FREE"!

Thats why I though if we could come up with a good solvent for this problem, we can 'soak & forget' and next week 'just rinse'.
I really dont want to replace 20 test tubes each yr.

BTW I just 'lost' 31 test tubes.. broken. Two boxes on the bench, and when I looked into box, 15 smashed in one box, 16 in the other. I am thinking that they either had a fall, someone dropped a brick on the boxes, or someone was bored and went to it with a hammer?
Tubes were still inside the honeycomb old-style cardboard boxes.

Estelle, I am going to try a few with vinegar.. at least thats cheap.

edited.. to make sense!

[kimmy]

I purchase our Plaster of Paris from Mitre 10 and is cheaper that Q stores and can get it as we need it.
We use vinegar in our cleanup after using Plaster of Paris - and I soak any items that have been placed in the PP to help clean them so give it ago .

Kimmy