Blue tones in mercury plates

[jgmotamedi]

What causes color casts on mercury-developed plates?

For the past 6 or so years of using mercury I have been occasionally haunted by plates with a blue cast. I have never been able to identify the causes and would appreciate help with problem solving.

I have attached my most recent example, from yesterday. It looks almost like a Becquerel plate, no? As best I can tell, this is not solarization, but something which causes the entire plate to turn blue. Could it be gilding? improper iodine/bromine balance? Something about my development? Humidity? Did I fail to make my ablutions?

The plate itself is slightly overexposed, and has slightly too much bromine in the balance. Here are the details,

70s First Iodine (Mostly gold with touches of rose)
30s Bromine (in silica gel, To mostly rose, with a touch of gold)
20s Second Iodine

It was exposed using a studio strobe, 9600ws @ f2.9
Developed at 70*C for 4:20
Gilded (about 2:30)

Thanks in advance!

jason

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[jgmotamedi]

I should also note that this is only an occasional occurrence for me, usually my plates are neutral or slightly warm. Last weekend’s plates were fine.

[greg7mdp]

Overexposure causes those blue tones (also called solarization). Try doubling the second iodine times and it will make it less likely.

[photolytic]

Jason,

Probably under development.

Due to the recent cold weather the top to bottom temp gradient in your mercury box may greater than usual.

Your rather long first iodine time (70s) also suggests that a lower temp in your darkroom may be the root cause.

I assume the 70degree was measured in the mercury itself whereas the temp on the plate surface may be considerably lower.

Remedy: When this happens, try increasing your developing time and or mercury box temp slightly.

[jgmotamedi]

Thank you John and Greg!

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