It's the Br€x/t tax.I've just looked at the sites of the suggested retailers of "Stay Afloat" putty (which is seemingly produced in the US):
France - Bigship = 17,90€ = £15.15
Spain - Francobordo = 19,99€ = £16.92
UK - Force4 = £24.95
(Marine Chandlery no longer seem to sell it.)
So, only an additional ~47%-65% markup here then!
Many years ago I worked for a firm that used to import industrial airless spray equipment. The machines seemed to have been packed by surrounding them in their cartons by plastic bags into which expanding foam was introduced. It expanded to completely fill the cavities around the machines and took up the shape of the box. It might be worth imvestigating the packaging industry to find foam that performs like this.
There is always some residual air in the tyre. It wont set in vacuum, inert gas, or water
