Australia's Science Forum

We have a prepared slide which has detatched from the cover slip. The specimen is on the cover slip. Is there a special glue that should be used to put the cover slip back on the slide? or is sticky tape over the top just as good? I've never had to worry about something like this before!
Rosalie

I think you need to use Canada Balsam. It is used as lenses cement and for mounting in microscopy, according to Chemwatch.
Carol

Hello again,
I had never heard of Canada Balsam before this. Liz very kinldy dropped some off to me. It is very thick though. Is this normal? Should I heat it to soften it? I thought using a toothpick to put it on the slide would be the go but it just pulled out like toffee. Next time I try I will also use gloves, as I got it on my fingers and it wouldn't wash off! I tried hot water, liquid soap, metho and finally it was eucalyptus oil which managed to dissolve it! I now smell like a tree, but at least I can use my fingers again!
Rosalie

Sorry, Rosalie - I was thinking as I drove away that it would help to have some instructions!
Having never used it myself (and the stuff could be up to 50 years old!), I can't offer advice, but I actually have been searching through older books and paperwork here - am sure I came across something on it recently. There's a brief mention in the DET science assistant's manual -
used as a media for permanent mounting because of it's resinous or gelatinous nature. A drop on top of the tissue, then the coverslip

I'll photocopy that for you, and also keep searching.

Try googling it!

FYI... I looked up the CSIS before I started playing with this stuff and it said OK for K-12, harmless etc... I just looked up the MSDS on the internet which I have attached. They don't tell the same story!
Rosalie

Hmmm - better change where I've got it stored!

Thanks, Rosalie

Rosalie,
Have looked up info on using Canada Balsam. "Balsam is applied to slide using glass rod. If it is too thick it can be diluted with a little xylene. Slides can be handled once balsam has hardened. Speed hardening by placing ....slide on warm hotplate, in a low oven or other warm place." (from a laboratory handbook dated 1978). Another reference says that Canada Balsam is "soluble in xylol, dioxane or trichloroethylene". (a handout from a 1998 Technicians Workshop here in Darwin)
Lyn.

P.S. No doubt the chemicals mentioned are no longer recommended for use. Would appreciate feedback as I think I have a container of Canada Balsam buried somewhere in the Biology prep room. If it's worthwhile I will think about resurrecting it.

Hi,

I have never used canada balsam before, but as it is xylene based it is probably quite bad and should be used in a fume hood or very well ventilated area. I have a recepie for a mountant called 'grey & wess' its very simple to make up, it will keep for years in the fridge and very easy to use. I have used it a fair bit at uni, its not quite as good as DPX which is also xyelene based, but its more than adequate fo what you need it for. If you want I can email you recepie and instructions for use.

Hi again,

Forgot to say that clear nail varnish will also do the job, not as well though and you have to be careful not to get too many airbubbles. what you should do to best avoid this is; place a generous amount of nailvarnish unto the COVERSLIP and then gently lower the slide onto it, turn it over and using a splint gently push on the cover slip to get ridd of the bubbles. This wont keep as well though, maybe only a few years.

Thanks for all your ideas. I think it will go in the 'too hard' basket (in this case the broken glass bin). We are needing new slides anyway so I'll just add a replacement for this one to the order and hope it gets approved for next year. Liz - do you want me to bring the Canada Balsam back?
Rosalie

No, we've still got plenty.

Thanks everyone - was very interesting to learn all that.

What is the shelf life? Does any one know, I have a few jars, but think they are very old 1977, perhaps put by for collection.

A quick google search came up with the "Sargent-Welch" Chemistry website and it said (among other things):

Balsam, Canada WLC94808-02 $30.10
Shelf Life - Indefinite
Storage Code - Flammable

There are probably more sites out there with more info. I can't really imagine anyone in our position using it these days when prepared slides are so readily available and this stuff is apparently so toxic!

Rosalie

Canada Balsam was the mounting media used a long time ago (a bit like tree sap or rosin).
It was replaced with DPX, the current mounting media, as it went brown with age.