"Rod Speed" wrote in message
...
I dont bother to preheat electric ovens except
when cooking pizzas, the oven heats up quickly
enough so that it makes no difference in practice.

Our electric fan oven takes about 10 minutes until the element switches off
when it gets to 180-200 deg C. When cooking something with a total cooking
time (assuming hot oven) of 30 minutes, that's a significant allowance you
have to make to cooking time if you cook from cold rather than from
pre-heated. My wife always cooks from cold and adds some indefinable extra
time whereas I like to get the oven at the required temp and cook for the
required time.


It does with pizzas because they are best done in
a stinking hot oven and it does take a while to get
an electric oven that hot, and the pizza itself heats
up quite quickly and cooks very quickly too, but there
isnt much else that is cooked in an oven like that.

Do they still use gas marks rather than degrees Celsius in gas ovens? I
haven't seen an explanation why gas ovens use these arbitrary numbers
rather than degrees (Fahrenheit or Celsius),

Basically because thats how they work, what you set
is the valve position, there is no thermostat like there
is with an electric oven. And there isnt that much that
need the oven temp set very accurately to cook it
properly either, its really just a few basic temps,
stinking hot, very hot, quite hot, quite cool, barely
warm for bread raising etc.

though I have some ideas why it might have happened.

Its pretty obvious really given how gas ovens work.

I've never come across a gas cooker with an oven which doesn't have a
thermostat and which relies on a constant flow of gas no matter whether the
oven is cold or up to temp. Even my mum's old 1962 cooker gave a big flame
when you lit it, which reduced to a smaller flame when the oven was up to
temperature. I'm not sure whether the temperature sensor reduced the gas
flow to a constant intermediate value when the oven was at temp, or whether
it activated an all-or-nothing control as for an electric cooker, where the
element either runs at full power or not at all, with the duty cycle varying
according to the temperature needed. If the oven had had a glass door I
could have watched what the flame did over time, without opening the door
and changing the very thing I was trying to watch.