If your tissue is a bit soft, then it is not completely dry. My tissue take a full 2 days to dry, and that's with a RH of 50%. What are you using for tissue support? What pigment? Is the pit from a bubble? Your pouring temp is probably okay. I consistently pour at 35C.
Yes, adding more dichromate lowers contrast. It also makes the tissue more sensitive, so exposures are shorter.
You should go to Sandy's yahoo forum and join up, as lots of carbon printers hang out there.
Oh, I see. I didn't think it can take so long for it to dry. OK then, I'll wait.
If your tissue is a bit soft, then it is not completely dry. My tissue take a full 2 days to dry
I don't know exactly what pigment it is. It's some black watercolor I happened to find lying around. I'm going to get some India ink one of these days. The support is a sheet of clear plastic. I'll try a sheet of watercolor paper tonight and see how it works.
That's strange. So, without dichromate the tissue is not sensitive to light, but if you use just enough dichromate for the tissue to be sensitive at all, then you immediately jump to the highest contrast possible? And then adding more and more sensitizer makes the contrast lower and lower? Well, it looks strange because I'm used to think about high contrast versus low contrast in terms of "deep blacks" versus "muddy blacks", and I expect more sensitizer to give deeper blacks, and less sensitizer to give weaker blacks. But I may be missing something.
Yes, adding more dichromate lowers contrast.
Thanks for the link.
Last edited by Vlad Soare; 02-15-2011 at 11:18 AM. Click to view previous post history.
I usually pour glop closer to 40 C, and let it cool slowly, without air drafts.
Do you let your glop sit for a hour or two to allow trapped air to escape? A vacuum pump can greatly shorten this process - 5 minutes.
A bit of alcohol in the glop helps with bubbles - use only pure ethanol or isopropyl (not cheap "rubbing alcohol" that may contain fragrance, colour etc.) I use yupo as my tissue backing, giving it a quick wipe with a barely damp cloth just before pouring the glop: scratches or dust on the surface can trap air, which subsequent shows upon dry-down. If you are adding glycerin to your glop, a very little goes a long way - it's easy to make never-dry tissue by adding too much
For pigment I am using lampblack water colour paint. Sometimes I use India Ink, but I prefer the neutral tones of lampblack. The amount of pigment used will also have an affect on contrast.
Don't use 99% isopropyl alcohol in the glop to get rid of micro-bubbles. Use 70%. If you use the stronger version, you will notice some of the pigment will congeil to the top. I
l let the glop sit in hot water for about an hour before I pour.
If I see any bubbles sitting on the top of the glop when pouring (I use a small glass beaker with measured amount of glop for each tissue), I spritz it with 70% isopropyl alcohol. If any bubbles appear on the tissue, I pop them with my finger. Some people use a rod to spread the glop around. I find this to be extremely messy and wasteful. Instead, I use my wife's comb. No glop wasted.
How long does it take for your tissue to set after pouring? A long set time will result in uneven distribution of pigment. It will settle to the tissue support side.
My room is 20C, so set time is about 5 minutes.
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I oft have wondered about the concentration/contrast relationship.
If you use 5% K-dich. then you are going to get low contrast. Perhaps this is because you have stepped over a critical point in sensitization, where your tissue is pushed onto a more "mellow"/straight section of the characteristic curve. With 2%, high contrast, the gelatin is just barely sensitized, so the points under your negative where no UV reaches are left w/ low exposure and low sensitization, thus very little hardening in those areas. In other words, there is a greater differential.
I feel like I'm explaining this after getting a cavity and my mouth is numb, only it's my fingers and I'm typing.... what I'm trying to say is, I'm struggling to find the words! I'd like to hear someone's more intelligent thoughts on this phenomenon.
If you are the big tree, we are the small axe
If your pigment is settling, it is likely coarse, or not well dispersed. Working WC paint with a drop of photo-flo with a pallete knife on a glass plate, adding water a drop at a time helps dispersion. I have never experienced 'pigment settling' after thorough blending.
Originally Posted by Andrew O'Neill
here is my list of probs and fixes.
bubbles in tissue---use a hot rod to smoothe over the surface, using magnetic frame for glop
streaks in picture---switch to tray sensitizing (easier and cheaper option)
frilling ---shorten soak time and increase tissue area size and safe area
developing streaks----larger safe area and lowered time and temp during dev
low contrast--- use a lower dichromate concentration. (.5%-1%) is great for fibre quality negs.
sticky tissue---lower sugar to 30g - litre (no need for clear plastic to protect neg)
hope this helps
Someone (the late Gordon Chappel) once explained perfectly to me the relationship between dichromate dilution and contrast -- and as soon as I walked out his door and started down the road, it left me completely! Oh, well.
I pour with the glop at 40C (plus or minus a couple degrees) in a cold (~16C) room. I pour directly onto plastic sheets -- moving the glop around with my finger tips to cover the plastic (actually used litho film). I wait perhaps 5 minutes, then tack the tissue onto cardboard and stand the cardboard vertically and have a fan blowing air (no heat) on it for the first 8 to 12 hours. This keeps the mold away. I wait for 48 hours (minimum) before printing. RH is usually around 60 to 70%. I get nice smooth surfaces.
I use no glycerin (damp climate), and more sugar than most folks (8% -- 60grams/750ml of water).
So many different ways to make good carbon prints. I use pigment concentration to control contrast -- as well as exposing/developing negs specifically for carbon printing. I have standardized on a stock solution of 8% Am dichromate, diluted 1:3 in acetone -- for a tissue for an 8x10 neg I use 5ml of the stock solution:15ml acetone. Not the "normal" way to work!
I use 100% isopropyl alcohol -- I do occasionally get some gelatin congealing on top, but it readily melts back into the rest of the glop. Lately I have been adding the 100% isopropyl alcohol to equal amount of water (used to clean out the last of the pigment from the container I mix the pigment -- lampblack water color) before adding it to the glop.
So many ways to make carbons! But pick one for awhile until you get a good grip on the process! best of luck!
PS -- I do not think "pigment settling" will be an issue -- the glop is too thick for the carbon particles to move significantly downward...especially once it starts to cool down (immediately after pouring). Just an opinion -- not based on any testing.
Last edited by Vaughn; 02-15-2011 at 03:41 PM. Click to view previous post history.
At least with LF landscape, a bad day of photography can still be a good day of exercise.
Ahhh! Don't tease us!
Originally Posted by Vaughn
Here.... crack your back in different place and maybe it'll come "flashing" back to you...
If you are the big tree, we are the small axe