What is that product under the saftey glass?

[bgadow]

I have used bits of popsicle sticks as spacers and you cannot tell there is a gap. I think you could probably go with less of a spacer if you wanted. The consensus from the last time this was discussed was that the original material was thin, like water, and was poured in after the edges were taped. I'm not sure where you would find such a product today.