Hello.
I have several 'bone' handled table knives that were handed down by my parents. I think they were purchased in the 1930's.
Last night I had cooked my supper (gas oven on Mk 6) and about five minutes after turning the oven OFF I had popped my plate back into the oven to keep it warm while speaking on the phone. Also on the plate was my 'bone' handled knife.
After about 2 minutes the knife handle spontaneously burst into a mass of flame and completely burnt out in a few minutes. I kept the oven door closed and the fire went out.
I now believe the handle could have been made of Xylonite (which is based I believe on cellulose nitrate).
I have now read that these can crack up or burn when heated, but are still widely sold in the antique market.
My question is - can I continue to safely use such knives, provided of course that they are not subjected to heat ? What about when put in hot water or left in the sun?
Should I dispose of them? It seems such a pity as I like them very much.
Many thanks.

Of course you should carry on using them your home is full of flammable items and if used correctly should not pose any fire safety problems just apply common sense in their use. Occasionally things can go wrong but that's life and hot water or left in the sun is unlikely to cause a problem I do not think you have any major concerns.

I have had three knives like the ones you describe for many years and I haven't had any problems.