Carbon Tranfer, rough exposure time for starting

edwoo11 · Jan 16, 2016

I am currently experimenting Carbon transfer, and looking around, i couldn't find any hint of exposure time that could work with my unit, I use a face tanning light bed (4 small tubes)
I know there is a lot of factors who can modify exposure time over that process, but it would be very welcome to know what would be a safe starting time with that unit, I really have no idea if i should go fo 5 minutes or more like 15 min, that would be an huge difference in result i guess...
Thank you so much for sharing your experience !

pschwart · Jan 16, 2016

Without a lot more details about your materials it's impossible to say -- tube wattage and spectrum, distance from the tissue, sensitizer and concentration, tissue recipe and thickness,
OHP or film, ... Just do a simple exposure test strip, or use a step wedge. Problem solved.

edwoo11 · Jan 16, 2016

Thanks for your answer, I will eventually do some tests, but this carbons tissue are too long to do to be wasting them, I will use a 5% solution of potassium dichromate, and i will probably expose at a 15 cm distance, I used the tissue recipe from altenativephotography.com, seems like the way to go when you begin.
For comparaison, I usually expose my Gum prints layers with my light source between 5-8 minutes, made with 13% solution.
It seems that exposition times are much shorter than gum prints, is that true ?

pschwart · Jan 16, 2016

edwoo11 said:
Thanks for your answer, I will eventually do some tests, but this carbons tissue are too long to do to be wasting them, I will use a 5% solution of potassium dichromate, and i will probably expose at a 15 cm distance, I used the tissue recipe from altenativephotography.com, seems like the way to go when you begin.
For comparaison, I usually expose my Gum prints layers with my light source between 5-8 minutes, made with 13% solution.
It seems that exposition times are much shorter than gum prints, is that true ?

Carbon transfer requires a *lot* of testing, especially when calibrating your materials and developing a workflow. A base exposure test, or even just a simple test strip, is about as basic as it gets, and only requires a very small piece of tissue. You will waste a lot more tissue -- and time -- if you choose to jump in and start making prints. If you can't be bothered, try 25 minutes at 7cm (3 inches).

Andrew O'Neill · Jan 16, 2016

You need to find the exposure that will give you a good black. It's called a min time/max black test strip. Make a print with this time and sensitizer strength. Adjust the sensitizer strength or density range of the negative accordingly. Will you be printing with film or inkjet negatives?

SMBooth · Jan 17, 2016

You really do need to do a test strip using the film base of choice.

edwoo11 · Jan 17, 2016

I will actually print from a glass plate negative 9 x 12 cm, Lumiere plate from ca. 1900... it's a small print... I'll start testing soon, thanks again !

pschwart · Jan 17, 2016

edwoo11 said:
I will actually print from a glass plate negative 9 x 12 cm, Lumiere plate from ca. 1900... it's a small print... I'll start testing soon, thanks again !

Take care not to ruin that plate! Use a sheet of mylar between the tissue and the negative to insure against sticking.

edwoo11 · Jan 18, 2016

Oh yes, that was my intention no way that this beautiful old emulsion get in direct contact wit gelatin !

Carbon Tranfer, rough exposure time for starting

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