Re: tips for using dry pigment
i got the P-F issues on friday (that was rather quick). thanks! i've been reading like mad since then.
sugar: i need the sugar to keep the curl out of the carbon tissue. i can't go below 60gr/liter. i've tried 40 and it was too little. one time i completely forgot the sugar and the result was a tissue that was almost unusable because of the curl.
i've read carbon formulas that called for a lot of strange stuff, honey one among them. i got the forumla with sugar from the sandy king article on unblinkingeye. i think the sugar is not supposed to do anything image-wise, but only keep the tissue flat.
whoops. i used the wrong word, "brick and mortar" for "pestle and mortar". of course i was not grinding it with a brick. i do use "grinding" to mix the pigment with the fluid, not to grind the pigment finer. i read a little about how it's done in painting and they all used a thing like a mortar and pestle to mix it.
i don't have problems mixing for gum, it's fine after just a little mixing with the brush. carbon is different, it's a lot more pigment (7gr for 500ml pigmented gelatin solution). when i put the water into the mortar, the pigment floats on top at first, then goes into the solution while mixing. i thought about adding a dash of alcohol to get rid of the surface tension of the water. it would make the process easier and less messy at the beginning.
i have to pre-mix the pigment in a little bit of fluid before adding it to the whole batch; mixing it in the 500ml of gelatin would be very messy and impractical. so i just mix it in a little bit of water, then add it to the whole.
i still haven't got a stouffer-step wedge, but i just prepared some carbon tissue to do the same testing with chart throb (digital step wedge and analysis program), i just did with gum printing. so, soon i'll be able to say more about that.
(i could post the scans of my comparsion of 5% vr saturated ammonium dichromate, if interesting to someone and not a complete bore fest. saturated is highly superior, step-wise. but i might try and use 5% for my shadow exposures)
Judy Seigel schrieb:
On Sun, 10 May 2009, firstname.lastname@example.org wrote:
i mostly use dry pigment for all my alternative processes. i started using it, because of a misconception that most alternative photo printers prefer it. later i learned that it just the opposite is the case. but actually i want to keep using it. it's way cheaper (i can buy 80gr of lamp black - which lasts a long time - for the price of on 15ml tube) and i already bought about ten jars. so far i haven't had any problems with printing gum (i put a little bit in a jar, mix it with gum and dichromate with a brush - no problems, no specks at all). but sometimes with carbon i get these specks (i'm not really sure if it's the pigment or the sugar in the mix (i use a rather high sugar content). i filter the carbon solution through a piece of nylon (? - the stuff women's stockings are made of), but still - mostly with the last tissue of the batch; of course the specks go down to the bottom. my normal procedure is to first mix the pigment with a brush and a dash of water, then grind it with a brick and mortar, then put it into the gelatine + sugar solution. i tried grinding the pigment in a little bit of gelatine solution, but using water was better. i once put a little big of alcohol (it's an old bottle labeled "brennspiritus" ("ethanol") i inherited from my grandfather, but i don't really know which kind of alcohol it really is, it's ages old) into the pigment mix and this had the good effect that the pigment sinks to the bottom, instead of swimming on top of the water. it makes the mixing a lot easier. what else could i add that would make the mixing and grinding easier. i haven't added any alcohol or whatever to my pigment mixes for alt. processes so far, because i'm afraid it could interfere with the process.