Fireproofing

[ss]

I have a small digital safe pretty useless as far as security is concerned however I would like to use it as the base to make a small fireproof locker. There wont be anything of real value in it, just maybe a bit of inconvienence if lost. I am going to use materials at hand so not going to go and buy special fireproof materials. I was thinking of casing the outside of the safe with a layer of plasterboard, then a layer of plywood, then a layer of plasterboard and finally a layer of 3/4 inch chipboard. Possibly with slight gaps between each layer. I`ll probably have it bolted to a cut to size paving slab to make it heavy. I would like to obtain maybe 1 hour fire proof and not too concerned about water damage.

Feasible or waste of time.

[N_Cook]

The traditional way of fireproofing stage scenery is a solution of borax ann boracic acid, IIRC. Quite impressive painting both sides of some cardboard, drying, and then trying to ignite it

[Chris Hogg]

You ought to include some decent fireproof insulation to stop the heat just toasting the contents of the safe without actually damaging the safe itself. Glass fibre of the sort used for roof insulation would probably do, but you can get refractory fibre insulation from potters' suppliers, or even use refractory insulating bricks, if you want resistance to higher temperatures. Another idea would be to use an intumescent paint either between your layers or over the outside.

[newshound]

That stops it catching fire, but what the plasterboard will provide is some thermal insulation so that the inside stays cool enough, assuming the fire brigade sprays the outside within half an hour or so.

Check eBay, there were quite a few "genuine" fireproof safes for reasonable prices last time I looked.

[Brian Gaff]

Wont the electronics or plastic bits melt so you cannot operate it? Brian

[ss]

Not bothered about that. As an aside it could be a good thing as its a Yale safe and so far I have 3 different methods (apart from keypad) I have used to access it, they are a piece of junk although to be fair I do some lockpicking as a hobby, just basic level.

[Martin Brown]

Feasible but you would have to experiment to be sure it would be fireproof. You have two problems in a fire thermal conduction and radiation transfer the latter tends to dominate in a big blaze.

You need a layered structure of materials that will not burn and on the outside of the object preferably an intumescent paint.

But you also need a reflective aluminium film (not an ideal choice since its melting point is quite low but easily available) radiation barrier on the inside and on the outside of the inner protected enclosure to minimise radiation transfer and a glass wool or better higher melting point rock wool lagging too.

Getting it right is something of an art form since the heat will always find the easiest path through any gaps to destroy the contents (and the dirty water used to put out the fire has a tendency to find them too).

[ss]

Thanks all thats given me some ideas.

[meow2222]

I don't know why you include ply. I'd cast the plaster fill in one lump, mixing some glass fibre in so it lasts longer. Steel inner, steel outer, plaster filling should last a while, the plaster absorbing latent heat as it chemically desiccates.

NT