Brilliant White: safe for darkroom walls?

[Jonathan R]

This is probably just a stupid question, but I guess it's best to be sure. I'm just about to paint the walls of my new darkroom. It occurs to me that Brilliant White contains optical brighteners. As far as I understand, these are basically fluorescent materials that absorb energy at UV wavelengths and re-emit it within the visible range of wavelengths. Since amber/red safelights are at the other end of the visible spectrum, can I safely assume that these optical brighteners are 'safe' in a darkroom?

[cliveh]

This is probably just a stupid question, but I guess it's best to be sure. I'm just about to paint the walls of my new darkroom. It occurs to me that Brilliant White contains optical brighteners. As far as I understand, these are basically fluorescent materials that absorb energy at UV wavelengths and re-emit it within the visible range of wavelengths. Since amber/red safelights are at the other end of the visible spectrum, can I safely assume that these optical brighteners are 'safe' in a darkroom?

Yes. However, quantum mechanics may not agree.

[RalphLambrecht]

white walls are perfectly fine for a darkroom. the only place where you may need black paint is around the enlarger.

[cliveh]

white walls are perfectly fine for a darkroom. the only place where you may need black paint is around the enlarger.

And the light trap entrance.

[Ed Bray]

What about blue walls, would safelight hitting them be reflected as unsafe light?

[cliveh]

What about blue walls, would safelight hitting them be reflected as unsafe light?

No and why would you want blue walls in a darkroom?

[cowanw]

They would come up as black since there would be no blue light to reflect. Red however would be a great darkroom paint, as it would reflect only safe light even if your safelight were unsafe.
Of course this is not a perfect world and few things emitting and reflecting are precisely as they seem.

[Ken Nadvornick]

The key point here is not what color the walls are, it's what color the walls reflect.

If all of the possible sources of light in a darkroom are safe (by whatever definition of "safe" is required for the process being performed), then by definition the walls—regardless of their color—cannot reflect an unsafe color. In this case any color will do. But white is preferred to spread the "safe" light around more efficiently.

The problems arise when one has white walls and the enlarger leaks imaging light. Or the doorframe leaks white light. Or the safelights aren't really totally safe. Then white walls only make the problem worse. In those cases black would be the ideal color, because you'd want to limit the spread of the "unsafe" light as much as possible.

Regarding the OP's question about UV causing optical brighteners to emit light from the walls, I've never heard of this being a problem. But the guaranteed solution would, of course, be to simply add UV light to the set of "unsafe" light colors and eliminate it from the darkroom the same as regular white light. And amber/red, not being UV, should have no practical effect.

Ken

[Ed Bray]

No and why would you want blue walls in a darkroom?

Perhaps if your Darkroom were dual use, say a bathroom or bedroom with Blue Walls but occasionally used as a darkroom. Not everyone has the space for a seperate darkroom. The question was just something that occured to me.

[cliveh]

Perhaps if your Darkroom were dual use, say a bathroom or bedroom with Blue Walls but occasionally used as a darkroom. Not everyone has the space for a seperate darkroom. The question was just something that occured to me.

A good point to which I agree.