Toaster Optics------?

I can't answer directly - I've not been able to source a graph. But I can give you some ideas. I've noticed exactly the same phenomenon

The heating elements of the toaster pump out a lot of light - although the heating is largely by invisible infra red. The point is that when you look at the toast you are seeing it by way of the light of the heating coils. The surface colour of an object is only perceived by way of the illuminant. So if you have a blue object and look at it with an illuminant that has no blue component then it will look black.

Normally this effect is masked by adaptation - you perceive the illuminant to be white. Ordinary tungsten lights are very red in colour but at night things seem roughly normal. What happens is the eye (well the brain actually) amplifies the blue and reduces its sensitivity to red. You only notice that something is weird when you take a photo without a flash. The picture comes out dull red.

The toaster is strange because you are looking at it with the rest of the room lit by a standard illuminant - daylight or a light bulb. This means that you get no adaptation so any colours inside the toaster will be false. I think I'll try an experiment of cooking some toast late at night with the kitchen light off. That would mean that my eyes would adapt to the sole illuminant - the heating coils in the toaster.

The thing that puzzles me is that brown is essentially a red colour. (You make brown light by shining a patch of orange and surrounding it with white light. Colourists say that brown is a contrast colour composed of orange and black.) This means that I would expect the brown on the toast to be less visible against the light bread under red light. Instead it is enhanced as you would expect if the scorch marks were blue.

I used to work for a company that produced colour measuring systems. If I still worked for them I would have taken a set of response graphs of various stages of toast for visible (not infrared) light. I think that would be interesting. Unfortunately I no longer have access to this kit.

This is an interesting question and makes me think. Sorry I don't have the answer you want.

Warning boring nerdy stuff follows. The full procedure is to get a spectral response giving reflectivity figures at 10 nm intervals between 380nm (blue) and 700 nm (red). Multiply each figure by the equivalent value of black body radiation for 1000C. This gives the light emitted by the toast in the toaster. You can then compare the resulting graph with a graph where the values are multiplied by D65 (standard daylight.)

Going further and allowing for the eyes' adaptation to daylight and the calculating the colours and colour differences is horrendous. There is no quick and easy way of describing that.

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