Anybody who kept fish, amphibians and reptiles before the 1970s will have tales of leaky aquarium tanks. Sheets of glass were held in place by metal frames made of angle iron or, cheaper, pressed steel. The glass was held by putty-like mixtures, with the pressure of the water inside compressing the putty against the frame. With time, the oils in the putty oxidised and hardened. Then, when the tank was emptied the pressure was released and small gaps appeared between glass and putty. The next time the tank was filled it leaked. It was tricky even to glaze a tank since the pressed steel frames were sometimes uneven and not exactly at right angles. Various proprietary putties were sold, Arbolite (still made for glazing windows) for example and many made a mess of frame, glass, hands, tools and anything surrounding. I once helped glaze a tank with a nasty black compound that even made its way up the arms. Tanks were also very expensive. The only size that could be afforded by many amateur aquarists was 24 inch x 12 x 12 (60 x 30 x 30 cm). In the mid 1950s that size cost £2.10s (£52 in today’s money) and that was just for the tank.
The invention by Dow Corning of silicone sealants changed all that. Aquarists first used it like conventional putty but the demonstration in the USA that sheets of glass could be joined by the sealant to make all-glass tanks killed off the metal tank frame although a few die-hards still thought it impossible that all-glass constructions could withstand the internal pressure and even demonstrated that some of the tanks broke—without realising the importance of a completely flat base. However, new metal framed tanks soon disappeared from the shops and, as each old-style tank leaked, were replaced by all-glass. Some metal-framed tanks remained in displays in shops. A few weeks before it closed, I had a look in Tachbrook Tropicals. The famous shiny chromium or stainless steel-framed tanks, I cannot remember which, were still in use to the end.
The first advertisement for Dow-Corning Aquarium silicone sealer I found in the issues of the Aquarist was in the May 1968 issue as ‘Now available in the UK’; but there was no mention of it being used to build tanks, just to stop metal-framed ones leaking. The UK was well behind the leading edge.