There are bubbles in the colossal squid tank!!! It’s not what we intended and we know that they may be interfering with your view of our big squid.
So why are the bubbles there and why can’t we get rid of them?
It’s not that easy to answer – you have to know a bit about the physics of bubbles, and what happens when you mix liquids which have dissolved gases in them. Te Papa’s Conservator Robert Clendon has been trying to explain it to me this morning, but my physics is a bit rusty – anyway here goes.
The tank that the squid is in contains a liquid mix of glycol and water. This is a preservative to stop the squid specimen from rotting. With a liquid that has dissolved gases in it the gas will start to come out and form bubbles. The bubbles then tend to stick to any tiny rough bits, or abrasions. Surprisingly enough the surface of the thick, acrylic lid of the tank is covered in these microabrasions. When you mix glycol and water together (as we’ve done) the water can’t hold as much dissolved air and bubbles start to form.
Usually we would leave the glycol and water mix for a good length of time to allow the bubbles to escape. When we first put the squid in the tank, filled it up and put the lid on there were hardly any bubbles at all – it was perfect!
However we had a problem with the tank at the last minute – one day before opening. We had to lift the lid off the tank, fix the problem and then top up the liquid. Time was against us to make the opening on Saturday and as a result…. we’ve got bubbles.
The bubbles are sitting under the curved lid of the tank. The small bubbles are gradually joining together (coalescing) to make bigger bubbles. When the bubbles are big enough they run off to the side of the tank and escape through the built-in tank vents.
The tank does have an internal pump system but it is very gentle as we don’t want to disturb the squid specimen too much. Robert is confident that the bubbles will go – but slowly. After all the whole tank and squid display is experimental and we are learning a lot through the process.
We’ll be watching the bubbles situation over the Christmas period and if it doesn’t improve we have a plan…. a cunning one.