How to break down calcium carbonate at home

Jan 2020
Kyiv, Ukraine
Hello, everyone.

I need to make several neat holes in seashell (basically the main component is calcium carbonate CaCO3).

First idea was to simply drill, but it turned out to be too tough - two bits were broken with a very little progress.

The internet readily suggests thermal decomposition. But relatively high temperature is needed (circa 850°C) and also heat moves slowly in all directions, which isn't controllable.

Then was en Eureka-moment - simply burn through with electric current! But of course excitement lived short - in solid state it doesn't conduct electricity.

Therefore all my hopes rest upon chemical means only.

1. They say acids will do. But the only acids I can easily get hold of are acetic (ethanoic, CH3COOH) in form of a vinegar and citric C6H8O7. Both are weak and diluted. It seems, vinegar can be boiled for a while to increase acid's concentration. This may work, but again liquids react in all directions, so it's also not very well controllable.

2. Also I have an acetone ((CH3)2CO), and this may somehow work too. Not sure though.

3. Then for some reason I've thought about potassium permanganate (KMnO4), which is also readily available. It also should react, it seems. But of course I don't know for sure and how intensive reaction will be if any. In form of powder it's more controllable, which is great.

So, basically the question is: could you provide some insights, useful suggestions or perhaps some other ideas?

Thanks in advance.
Sep 2018
The mechanical method would be to grind through (rather than drill)
proper grinding bits (for your drill) can be obtained,
but a bit of grinding paste, on the end of a (sacrificial) wooden stick might work.

Using acids might be possible, but I suspect it could be difficult to constrain the hole
to be exactly where and how big you want it.

Also, as you yourself point out, the readily available (safe) acids will have very slow actions
more powerful acids are available, but must be used with considerable care.
Apr 2015
Dentists drill holes in calcium carbonate 'shells' all the time with a dentist's drill!
Sep 2018
I think that if you look at the bit in a dentists drill, you will find that it is essentially a grinding bit (rather than a cutting bit).
I suspect that the OP might have been trying to use a drill intended for metal (which would be a cutting bit).
A drill intended for masonry might be better, but would probably be difficult to find in the appropriate (small) size.

Drill bits intended for drilling holes into ceramic are available, and these would (probably) work well.
Sep 2018
When I was young, (many years ago) my usual dentist was unavailable so I was seen by one of the other dentists in the partnership.
This dentist used a very old fashioned drill arrangement, driven by a series of rubber belts and pulley wheels from an electric motor.
That drill was definitely a grinder!
It was actually not as dreadful as your imagination might suppose it to be, but I certainly remember the experience...

I'm going to the dentist in a few days, I will ask how his modern drill works...
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