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I want to make attractive signs to point to the locations of fire shelters for our community, in a fire-prone area. I want something that would be visible to rescuers after going through a bush-fire of 1000 degree celsius or so.

The simplest approach would be to cut the signs out of sheet metal. But I'm wondering if anyone has ideas for materials that might retain color?

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    +1 for the general idea. Having watched a copper garden grill chimney hat literally melt and drop down after someone (not me!) stuffed the grill chamber below with thin wood planks, I suggest you really do your homework on fire-proof materials.
    – Stephie
    Commented Oct 8, 2017 at 20:18
  • Are you creating signs for commercial sales? If so, you will need to check to see what the fire code standards are for materials and visibility, etc. Anyone interested in purchasing the signs (cities, counties, etc.) will need to comply with all fire code standards. Even if the signs are just for your neighborhood, you should check with a lawyer to assess liability. In addition to directing rescuers to potential survivors, the signs also imply that people following the signs to the fire shelter will be safe from the fires. Hopefully, this would be the case, but you can't really guarantee it.
    – user1798
    Commented Oct 11, 2017 at 1:26
  • No, this is for signage within a private property. That's not to say fire code standards might not be useful though, if they identify a range of materials as acceptable. We've been explicitly asked by the local fire authority to establish the signage, but they aren't much help in terms of how best to construct the signs.
    – mc0e
    Commented Oct 11, 2017 at 14:56

2 Answers 2

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Since fire coats the things it can't destroy in black opaque soot, it doesn't really matter if the colors underneath survive... they won't be seen until after someone cleans the sign, after the fire is over.

I would suggest using the sign's shape to convey its meaning. That way, even when it is totally blackened and silhouetted against a wall of flames behind it, its meaning will still be clear.

Fire Shelter Sign With Meaning Depicted By Sign-Shape

As for material suggestions, I would consider aircrete ( a mixture of concrete with a foaming resin ) which is extremely fireproof. Also, there are a lot of additives that you can add to concrete (and by extension aircrete). Gypsum or Quartz powders will make the sign reflect flashlight beams. Dyes and colored stones can be added to increase the sign's unsooted visibility and some to those dyes absorb sunlight and glow in the dark. The sign can either be made relatively attractive or garishly noticeable with very little additional effort.

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  • Looking at aftermath footage (e.g. search "black saturday aftermath" on youtube), I don't think it's a given that things will be covered in soot, though it's a risk. I'll check out aircrete
    – mc0e
    Commented Oct 9, 2017 at 7:53
  • Note that my concern is primarily for people to be able to find survivors after the fire. If there's a backdrop of flames, it's too late to be reading signs.
    – mc0e
    Commented Oct 9, 2017 at 11:40
  • This would also work against a backdrop of sky, but not so well against a backdrop of charred trees. It may still be a good idea.
    – Chris H
    Commented Oct 9, 2017 at 15:52
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Steel is cheap and easily laser- or machine-cut (because it's so common, any machine shop can handle it). It's about as fireproof as anyone is likely to need (woodburners are often made of it). Stainless is nice but plenty of grades of steel will only form surface rust for many years in most climates. You can blacken stainless steel or contrast stainless with blackened mild steel to get monochrome patterns, but the masking might be interesting.

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  • I'm currently pursuing the laser-cut steel approach. I wouldn't be confident that patinas would stay in place through the sort of heat we'd see in a bush-fire, but it does seem likely that different metals would remain visibly different and provide a contrast.
    – mc0e
    Commented Nov 7, 2017 at 6:41
  • I think the patination would survive though maybe change colour a little. The rest of the sign may also end up patinated (but not in the same way) reducing the overall effect (I ended up getting some stainless quite hot the other day and saw discolouration). Another option might be to use a thin sheet of copper or brass (check the melting points) on top of the steel - but use steel fasteners or weld/braze it on top, not aluminium pop rivets.
    – Chris H
    Commented Nov 7, 2017 at 7:48
  • aluminium is definitely out. copper is a bit dubious, and brass more so.
    – mc0e
    Commented Nov 8, 2017 at 16:08

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