plate sensitizing difficulties

[Dagwood24]

Hello, after many years with only limited success in making dags, I have a question perhaps some of the more experienced practitioners can answer. Yesterday I attempted to sensitize some plates, they (three) turned pale yellow in about a minite but even after five minites they did not cycle to any other colors. The edge of one did start to turn magenta. Any opinions as to what is or isn’t happening? Temp was about 85, zero humidity.

[newone2010]

Hi Dagwood 24,

I have little experience in making D’types too,but I think your problems maybe caused by the light of your darkroom.Which kind of your light?

I made mistake in the light sometimes.I forgot to turn off the PL Lamps when I sensitized few plates.The plates after Br looked like pale with a little blue,and did not change to any other color forms when I try to add more time.

Hope this can help you,

Li

[photolytic]

Dagwood,

Unless you forgot to put the iodine in the fuming box, your plates may be turning to the 2nd yellow after only one minute at 85F (30C). If you are not looking at the color of your plate frequently (10-20sec) the color may just be jumping from one cycle of yellow to the next.

I don’t think having too much light is the problem but rather not having the right color light.

Looking at the plate colors using a white colored light shining on a white surface is best.

Even with a white light on stray light from a red colored safelight makes judging the shifting plate colors more difficult as the colors look warmer (rosy).

The color changes during the bromine fuming are more subtle, shifting towards a rose to blue tint but not back to yellow again. The ultimate effect of bromine fuming is best judged after a second fuming with iodine.

[Andy Stockton]

I have had trouble distinguishing color cycle changes when looking directly at the plate. The “white surface” method photolytic mentions above is very helpful. I add to the method by pointing my white light at a fumed plate and an unfumed plate at the same time. Just place the plates side by side. I reflect the light from both plates onto a piece of white card stock taped to the side of the fume hood. Having a comparison plate made it very easy for me to see the color difference.

[photolytic]

Charlie Schreiner has some good plate fuming colors posted on his newdag.com site but here are a few of my own.

I fumed this plate about a year ago and kept in away from the light.

 

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[Dagwood24]

I thank you all for the fast replies. Will try again (what on earth keeps us going?) I have included a photo of my iodine crystals in their ground glass dish, do you think this is enough?

Saw the large plate exhibition in San Francisco. Never saw so many well done large plates in one place in my life. Truely the work of a very gifted artist.

Chuck Diephuis/Dagwood24

[Dagwood24]

Here’s the iodine dish.

 

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[photolytic]

Not enough Iodine. For faster fuming you need enough iodine to cover the bottom of the dish.

Your first fuming cycle may have exhausted the iodine vapor above the crystals.

You might try waiting several minutes before putting the plate back in the box for more fuming. That will allow the vapor to build up again. When the iodine vapor is restored it will react with the silver. The rate of the reaction of the iodine with the silver surface, which some are calling “uptake”, is actually a kind of corrosion of the silver surface. As such it is affected by the polish of the plate but is mostly dependant on the temperature and the iodine vapor concentration.

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