Double layer glass question

[Lillee]

Hi all,

I am building an above ground pond and want to put in a small viewing window, no larger than 12inches by 8inches (mainly for guaging fish growth and see water level). I have alot of 6mm glass lying around and have cut pieces myself to suit. My question is:

Is 2 pieces of glass sandwiched together, edge to edge to make a single 12mm pane stronger than a single 6mm pane? Yes I know it's weaker than a single 12mm pane but how much so? is it equivalent to 8mm glass? What if I used 3 x 6mm for the window?

Or should I not bother and go with 1 12mm piece?

Or should I just go buy a 10mm acrylic piece?

Any advice would be much appreciated!

 

[karak]

What depth of water is it going to be in?. they use 6mm for up to 18"

 

[Lillee]

What depth of water is it going to be in?. they use 6mm for up to 18"

Thanks for reply, this will be at the top of the pond so the waterline will be visible in the window, so max depth 270mm (3 x 90) or 360 (4 x 90 as I am using 90 x 45mm beams in the construction of the pond).

I worked out that there would be approx 800Litres of water pushing up against the glass which made me rather nervous so I walked out at lunchtime and purchase a 15mm perspex sheet instead to do the job instead

Thanks anyway!