When Borax [Na2B4O7.(10)H2O] + Sodium Hydroxide [(2)NaOH] are fused together sodium metaborate [(2)Na2B2O4.(4)H2O+(3)H2O]is formed Kodalk has alkaline properties between those of Borax and sodium carbonate. Borax at 2% solution yields pH 9.4 and Sodium Metaborate at 2% yields pH 10.4 Sodium Hydroxide is very caustic alkali at pH 13 Jonathan Ayers [mail1@xxxxxxxxxxxxxxxxx] -----Original Message----- From: pure-silver-bounce@xxxxxxxxxxxxx [mailto:pure-silver-bounce@xxxxxxxxxxxxx] On Behalf Of Jeffery Smith Sent: Friday, May 04, 2007 2:22 PM To: pure-silver@xxxxxxxxxxxxx Subject: [pure-silver] Re: 'Ripening' procedure for developer? Well, this was a circular search. I had heard that some people used Kodalk instead of borax. I went to PF, which states the following: "Kodak has changed the name Kodalk; to Balanced Alkali; - this is their proprietary name for sodium metaborate." Inasmuch as sodium metaborate is borax, I'm glad I didn't order Kodalk. Richard, do you know of other alkaline activators for the developer? Jeffery Smith New Orleans, LA http://www.400tx.com http://400tx.blogspot.com/ -----Original Message----- From: pure-silver-bounce@xxxxxxxxxxxxx [mailto:pure-silver-bounce@xxxxxxxxxxxxx] On Behalf Of Richard Knoppow Sent: Friday, May 04, 2007 4:02 AM To: pure-silver@xxxxxxxxxxxxx Subject: [pure-silver] Re: 'Ripening' procedure for developer? ----- Original Message ----- From: "Jeffery Smith" <jls@xxxxxxxxxx> To: <pure-silver@xxxxxxxxxxxxx> Sent: Thursday, May 03, 2007 6:29 PM Subject: [pure-silver] Re: 'Ripening' procedure for developer? Developers like D76 change for the worse over time. One of the problems is pH change, which affects the activity of the developing agent. I have been using divided D76, which is a bit more stable. The first bath allows inactive developer to soak into the emulsion. Time and temp aren't important. Transferred to the alkaline bath (borax), the developer in the gelatin becomes active until it is exhausted. The first bath can be reused over and over. The 2nd bath (cheap) is discarded. But I am getting to the point that I don't trust developer unless it is fresh. I have bought about 5 kits of Paterson citric acid developer. By the time it reaches the states and gets into my darkroom, it is DOA. Jeffery Smith New Orleans, LA http://www.400tx.com http://400tx.blogspot.com/ D-76 is an interesting case. Shortly after the formula was released in 1927 it was discovered that its activity increased slowly. The real cause took decades to discover but the immediate cause was a rise in pH. In 1929 a research paper was published by Kodak Research Labs describing the problem and a solution for it along with data on a great many variations of the formula. The cure was to buffer the solution by using a combination of Borax and Boric acid. The data in the paper shows the the developement time for the original formula for a given gamma was reduced to a bit more than half the time after storage for about a month. For the buffered version there was insignificant change over the same period. It was discovered much later that the mechanism for the pH rise was a slow reaction between the Hydroquinone and the Sulfite which produces a small amount of Sodium Hydroxide. Developers which do not contain Hydroquinone do not suffer from this problem. It is likely that the pH of many M-H developers are high enough to begin with that the small rise from this reaction is of no significance. The packaged version of D-76 has been the buffered type for several decades. For those interested the formulas are as foll Standard D-76 Water (at 125F or 52C) 760.0 ml Metol 2.0 grams Sodium Sulfite, dessicated 100.0 grams Hydroquinone 5.0 grams Borax 2.0 grams Water to make 1.0 liter D-76d Water (at 125F or 52C) 750.0 ml Metol 2.0 grams Sodium Sulfite, dessicated 100.0 grams Hydroquinone 5.0 grams Borax 8.0 grams Boric Acid, Crystaline 8.0 grams Water to make 1.0 liter This will have the same activity as the original formula when fresh. The activity of the buffered developer can be varied over a wide range by changing the relative amounts of Borax and Boric Acid. Crystaline Boric Acid should be used because the granulated variety dissolves with great difficulty. A note about packaged Kodak products: Kodak has a large number of patents for the stabilization of the ingredients of both powder and liquid developers and other chemistry. They also seem to have paid a lot of attention over the years to sequestering agents, etc., to make their packaged chemistry as nearly immune to water quality as possible. No doubt other manufacturers have done the same. Other than a couple of bad experiences with Xtol I have never had a failure with any packaged Kodak product. There is a limit of lifetime to the materials in the paper packets. The packages are made of a paper lined with metalized plastic. They were supposed to be completely impervious to air and moisture but obviously are not. I don't know the mechanism of the failure but suspect it is micro-cracks in the metalized plastic liner. In any case, I've opened very old packages of Dektol which looked like coffee grounds and smelled like dead mice. Not nice. The very old stuff in hermetically sealed tin cans seems to last forever. A couple of years ago Kodak got rid of the paper packages in favor of all plastic ones with one less seal. Its too soon to know how well these hold up for long time periods. Some liquid concentrates do not have unlimited life. For instance, rapid fixer will eventually decompose. Again, I don't know the mechanism but it may be due to leakage of air through the plastic containers and is at least partly due to the inherent instability of the chemicals although they are treated to improve their stability. --- Richard Knoppow Los Angeles, CA, USA dickburk@xxxxxxxxxxxxx ============================================================================ ================================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there. ====================================To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there. 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