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brucep
18-Dec-2014, 09:17
Can anyone offer any suggestions about the cause of these lumps (i'm assuming they are bubbles as I filter through fine cheesecloth) that appear in my shadow areas? and better still, how to avoid them.

They start to reduce in size and number from about band 4, and although an odd one appears elsewhere, they are only visible with a magnifying glass. It appears that they are related in number and size to the density.

126835

Thanks for any help.

Bruce

Andrew O'Neill
18-Dec-2014, 10:19
Try 1. backing off on your exposure a bit, or 2. tissue soak time, or 3. reducing development temperature, in that order. For me, it was the first one. What are you transfering onto?

brucep
18-Dec-2014, 10:53
15 mins exposure was a bit long as I just lost adequate separation between band 1 and 2, but even at 8 mins the lumps are present. Tissue soak time was 90 secs in room temp (21c) water that had stood for 2 weeks. Transfer was onto yupo, with light brushing to ensure I had no fine bubbles on it.

Andrew O'Neill
18-Dec-2014, 11:00
Yupo can be challenging to transfer onto. Did you give it a good washing in detergent?

brucep
18-Dec-2014, 11:14
No, didn't use detergent, just soaked in hot water and hung up to dry a couple of weeks ago.

Jim Fitzgerald
18-Dec-2014, 18:12
What tissue? Did you make your own? I feel that the soak time is to long and temperature is to high. My soak is for about 40 seconds and the water is cold, always under 60 degrees. If the hot water development is to hot and the tissue to thin I think that may be the problem as well.

sanking
18-Dec-2014, 19:55
Are you using glucose in place of sugar in the tissue formula? If so, would be interested to know your reasons. I think this substitution would be almost sure to change the normal soak times we would expect with for a given concentration with sugar, and I have no idea in which direction since there is almost no information in the literature about this?

Sandy

brucep
19-Dec-2014, 08:35
Are you using glucose in place of sugar in the tissue formula? If so, would be interested to know your reasons. I think this substitution would be almost sure to change the normal soak times we would expect with for a given concentration with sugar, and I have no idea in which direction since there is almost no information in the literature about this?

Sandy


No, just me interchanging sugar and glucose incorrectly. It is definitely common old sugar.

brucep
19-Dec-2014, 08:46
What tissue? Did you make your own? I feel that the soak time is to long and temperature is to high. My soak is for about 40 seconds and the water is cold, always under 60 degrees. If the hot water development is to hot and the tissue to thin I think that may be the problem as well.


The tissue is home made about 1mm thick using 1.2%Windsor and Newton water colour lamp black and 8% 250 bloom gelatin sensitized with 0.5% das.

Just tried again with 10c mating water and hot water allowed to cool to 40c to develop test strip. Reduced exposure to 12mins but results are exactly the same.

Will try fixed out photo paper and some sixed rag paper next to see if it is the yupo causing the bubbles.

Bruce

windij
19-Dec-2014, 09:05
In my experience bubbles are the result of either an improper transfer technique or excessively hot water during development. If you're making your own tissue the addition of isopropyl alcohol to the glop will help reduce bubbles. I've also had lumps show up when I use certain watercolor paints, even when filtered multiple times. I have no idea what causes this, something is causing the pigment to flocculate (clump together). I just stopped using that brand of pigment.



Jason

sanking
19-Dec-2014, 12:04
I would recommend working out your transfer procedures with RC silver papers as they are about as reliable as it gets for carbon transfer. If you can not make a good transfer on RC silver papers something in the methodology is way off.

Soak time is dependent on several factors, including water temperature, the percentage of the glop, sugar loading, and coating thickness. In my work, which is primarily with tissue made with a 10% gelatin (250 Bloom gelatin) solution, with 0.5% sugar, and poured to a wet height of about 1.0 mm, I soak the sensitized and exposed tissue for about three minutes in the summer in water at about 72 F, and four minutes in the winter in water at about 66 F. My experience is that too short of a soak can be as bad as soaking too long.

Sandy

Jim Fitzgerald
19-Dec-2014, 20:35
The interesting thing about carbon printing is the variables. Where I live by the beach, my soak time is short in comparison to what Sandy does in his work flow.
Generally my results are consistent. No bubbles. I think the temp of the development water is a problem.

Take Sandy's advice and use RC paper for the transfer. Most of all establish a repeatable work flow and beware of "Cycles of the Moon"

John Jarosz
20-Dec-2014, 07:41
My experience is that too short of a soak can be as bad as soaking too long.

I have always felt this is true, but I have no hard data to confirm it.

+1 on the "Cycles of the Moon".

sanking
20-Dec-2014, 11:56
I have always felt this is true, but I have no hard data to confirm it.

+1 on the "Cycles of the Moon".

Yes, it is easy to advise that soaking too short is as bad as soaking too long, but that begs the question what is long enough. As Jim suggests, we can really only learn from a consistent work flow where all of the important parameters are identical (or as similar as possible).

That said, the major determinants in soak time are, 1) tissue coating thickness, and 2) amount of plasticizer (sugar) and/or humectants (glycerine) added to the pigmented gelatin solution, and 3) temperature and time of the soak bath. Each can have a major impact on how fast the tissue absorbs water in the mating bath.

One of the characteristics of carbon printers is that are by nature inclined to experimentation for its own sake so they tend to not listen to the advice of others and set out on their own personal adventure in formulating the pigmented gelatin solution, and in pouring and sensitizing it. This creates a condition akin to chaos in terms of a common approach, which is good in that we are all right every now and then, and can always blame our failures on events beyond our control!!

But there is truly something awesome about the elegance of the process, and at heart its basic simplicity. It is sad that many photographers will die having never made a good carbon print, or worse, never even seeing one.

Sandy

Jim Fitzgerald
20-Dec-2014, 22:33
Yes, it is easy to advise that soaking too short is as bad as soaking too long, but that begs the question what is long enough. As Jim suggests, we can really only learn from a consistent work flow where all of the important parameters are identical (or as similar as possible).

That said, the major determinants in soak time are, 1) tissue coating thickness, and 2) amount of plasticizer (sugar) and/or humectants (glycerine) added to the pigmented gelatin solution, and 3) temperature and time of the soak bath. Each can have a major impact on how fast the tissue absorbs water in the mating bath.

One of the characteristics of carbon printers is that are by nature inclined to experimentation for its own sake so they tend to not listen to the advice of others and set out on their own personal adventure in formulating the pigmented gelatin solution, and in pouring and sensitizing it. This creates a condition akin to chaos in terms of a common approach, which is good in that we are all right every now and then, and can always blame our failures on events beyond our control!!

But there is truly something awesome about the elegance of the process, and at heart its basic simplicity. It is sad that many photographers will die having never made a good carbon print, or worse, never even seeing one.

Sandy

Sandy, I could not agree more. I knew from the moment I saw first carbon print what my destiny was as a photographer. How great is that! Seeing a great carbon print is something special. Making one is heaven.

brucep
24-Dec-2014, 01:54
No, just me interchanging sugar and glucose incorrectly. It is definitely common old sugar.

Interestingly, in the book Photography Theory and Practice by Clerc, he actually uses a mixture of Loaf Sugar (which I believe to be the same as granulated) and Glucose syrup, so using Glucose must have some positive benefit unless it used to be much cheaper than loaf sugar and you could get away with using some to save money.

Bruce

Jim Fitzgerald
24-Dec-2014, 09:04
The advice I give all of my students is follow my directions and don't ask why. Learn my established procedures. Once you have control of the mechanics of the process you can start asking questions why? The what if's come later after you can transfer and make beautiful prints all the time.

brucep
24-Dec-2014, 10:37
My comment was in response to Sandy's comment about not knowing what effect using glucose would have on the process rather than planning to try it.

I would say though, that without understanding as much as I can about the process I would be making wild changes to troubleshoot problems rather than targeted changes based on logical reasoning.

Anyhow, the same book I quoted above recommends mating at room temp if the room cannot be kept at 65F to stop the formation of micro bubbles as the water warms up, and to soak the tissue until it stops having any tendency to curl. Just tried this, which was a 3min soak at 22c and a perfect transfer with no lumps or holes😀.

Very happy.

Bruce

sanking
24-Dec-2014, 10:47
Interestingly, in the book Photography Theory and Practice by Clerc, he actually uses a mixture of Loaf Sugar (which I believe to be the same as granulated) and Glucose syrup, so using Glucose must have some positive benefit unless it used to be much cheaper than loaf sugar and you could get away with using some to save money.

Bruce

People have experimented with dozens of plasticizer type substitutions for cane sugar, from karo to molasses to sorbitol. None work any better than sugar, so why bother since pure cane sugar is one of the most commonly available substances on the planet, and *any* substitution in a pigmented gelatin solution can result in unexpected results. People in very arid climates (less than 25% RH) may also need a humectant in the pigment, and for that glycerine is as good as any. Where I live the RH rarely goes below 30% RH, and any glycerine added to the glop is more of a nuisance than help.

Did I mention that *any* substitution in a pigmented gelatin solution can result in unexpected results?

Sandy

sanking
24-Dec-2014, 10:55
Anyhow, the same book I quoted above recommends mating at room temp if the room cannot be kept at 65F to stop the formation of micro bubbles as the water warms up, and to soak the tissue until it stops having any tendency to curl. Just tried this, which was a 3min soak at 22c and a perfect transfer with no lumps or holes��.

Very happy.

Bruce

Congratulations on the good transfer. I used to believe that more than two minutes at 72 F was too long for the mating bath. However, I have come to understand that many of the problems we experience in transfer are due to dichromate degassing, which is alleviated by a fairly long soak.


Sandy