how hot does wood have to get before it catches fire on its own?

[NCEric]

I'm thinking about building a fairly primitive solar oven, basically just a thick wooden box with a couple layers of glass to trap the heat from the sun for cooking and maybe some reflectors to increase the solar radiation.  I'm thinking about charring the wood on the inside of the box because a dark surface would presumably absorb more solar radiation.  What I'd particularly like to know is whether there's any risk of catching an oven like this on fire.  I'm guessing the very hottest a solar oven like this might reach under optimal conditions would be around 400F, but that's just a guess, and maybe particular parts of particular surfaces would get substantially hotter, but I don't really know.  What do you all think about the risk of a solar oven catching fire?

[NewYankeeSawmill]

Well, I do recall reading in a book that paper burns at 451-deg Fahrenheit.... So, maybe 450-ish? Maybe go the other way and line it with a reflective material? You could staple those plastic emergency blankets up pretty cheaply?

[doc henderson]

and I think that was paper and is close.  Look up boy scout carboard oven.  It used charcoal or coals from a fire to bake biscuit and stuff.  it was lined with aluminum foil.  wood that is dry is an insulator so with the solar reflection it will stay cooler.  the black char might start as charcoal starts easier than raw wood.  is this for fun, or long-term use  i would start simple and make it more durable if it works as intended.

[TreefarmerNN]

According to https://fireproofdepot.com/what-temperature-does-wood-ignite/
the ignition temperature of wood is 480-530 f. 

[fluidpowerpro]

Well, I do recall reading in a book that paper burns at 451-deg Fahrenheit.... So, maybe 450-ish? Maybe go the other way and line it with a reflective material? You could staple those plastic emergency blankets up pretty cheaply?

Fahrenheit 451 is the title of one of my favorite science fiction books. The author was Ray Bradbury.

[sprucebunny]

Just Don't ask the wacky insurance guy I met who said pine Could ignite at 180F :rolleyes:


I've been kind of paranoid ever since. Some serious internet sluething is probably in order !

[Ianab]

To get sunlight to ignite wood you would have to focus a LOT of sunlight into a small area. Think on the scale of a magnifying glass, maybe 4" across, but focusing down to a spot that's on 1/8" across. That will ignite wood no problem. 

This page has some examples, current, historical and legend. 
https://en.wikipedia.org/wiki/Concentrated_solar_power

A legend has it that [color=var(--color-progressive,#36c)]Archimedes[/color] used a "burning glass" to concentrate sunlight on the invading Roman fleet and repel them from [color=var(--color-progressive,#36c)]Syracuse[/color]. In 1973 a Greek scientist, Dr. Ioannis Sakkas, curious about whether Archimedes could really have destroyed the Roman fleet in 212 BC, lined up nearly 60 Greek sailors, each holding an oblong mirror tipped to catch the sun's rays and direct them at a tar-covered plywood silhouette 49 m (160 ft) away. The ship caught fire after a few minutes; however, historians continue to doubt the Archimedes story.

Also look up sous vide cooking. which slow cooks meat at under 160F. So you don't have to get ~400F to cook food, but you need a vacuum sealer.  

https://en.wikipedia.org/wiki/Sous_vide

[sprucebunny]

I thought about this some more.

I have an electric smoker oven big enough for a small turkey. It has small pockets that hold smoking chips. I don't soak them. They smoke and turn to ash at 325 and above.

[NewYankeeSawmill]

Fahrenheit 451 is the title of one of my favorite science fiction books. The author was Ray Bradbury.

Yessir! I was trying to be coy...   All of his books should be must-read. Unfortunately kids today do not cover those in English Literature anymore. I'd digress, but that has nothing to do w/ @NCEric 's kiln topic!

[doc henderson]

Wood Flash Point, Ignition Temperature & Combustion Temp - Fireproof Depot

spruce, it might have been 180C

[Ianab]

There are various heat resistant wall boards available. Generally used to put behind a wood stove to protect the wall and greatly reduce the fire risk. Something like that would work in this scenario?