Insulation for Fireproof Safe

[djed]

I actually found the ratio I referenced in an old hall patent. I also read that the alum was inserted in the mix as large pieces rather than as powder (which is what I purchased). I wasn’t aware of the tin boxes. That still leaves me wondering what they used. I understand these weren’t necessarily meant to be burglar proof but the original insulating material is harder than the mix I created.

[djed]

Disappointed - the plaster/alum/lime mix shrunk and separated from the safe wall (so that it is now floating as a chunk of plaster in the large hole I filled).

Not it sure which direction I’m headed. Suggestions are welcome.

[Chubby]

Fill the void with more of the same.

[djed]

Looked online and found a suggestion to add bonding agent (looks a lot like white glue) to the water that I mix with the plaster. I also kept the mix closer to the original water mix ratios resulting in a thinner plaster mix. The mix could only be added to the bottom of the safe wall since it would run out otherwise. After a few days of dry time, the insulation now seems to be holding and not shrinking/cracking. I hope this helps someone in the future tackling this same issue.

[Arcade Al]

Looked online and found a suggestion to add bonding agent (looks a lot like white glue) to the water that I mix with the plaster. I also kept the mix closer to the original water mix ratios resulting in a thinner plaster mix. The mix could only be added to the bottom of the safe wall since it would run out otherwise. After a few days of dry time, the insulation now seems to be holding and not shrinking/cracking. I hope this helps someone in the future tackling this same issue.

You mean PVA as the bonding agent?

[Chubby]

PVA will help to stop such things cracking. You don't need much.

We used to add it to the concrete in which floorsafes were installed. When testing concrete samples it was noticable that those with PVA added were a little bit tougher than the others.

[djed]

This is the stuff I used:

https://www.homedepot.com/p/Quikrete-1-Qt-Bonding-Adhesive-990214/100318541

I also brushed this on the area into which the plaster mix was going to be poured.