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Article: Borax Project

  1. #1
    gainer's Avatar
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    Borax Project

    My Borax Project
    Borax is useful in many ways. Some of us worry about the purity of the commonly and cheaply available 20 Mule Team Borax. There is another concern in cases where accuracy of weight is important. Borax has 2 possible states of hydration, decahydrate and pentahydrate. If a 100 gram sample of pure borax has pentahydrate and decahydrate mixed, the assay will show a greater weight than 100 grams. If 5 grams of a 100 gram sample are the pentahydrate and the rest the decahydrate, no matter how purely the saple is composed only of sodium tetraborate and water of hydration, the assay will show 101.5 grams of the decahydrate. There is no way you can tell at time of collecting a sample from a large batch of pure mixture how much of each hydrate you are getting.
    A common solution to both problems is literally a solution. A saturated solution of borax at a given temperature contains a known weight of borax expressed as the decahydrate, whether the solid used to make the solution was penta- or decahydrate. If the solution was made saturated and separated from the solid at a low temperature, it will have a constant weight of borax per unit weight of solution at any (reasonable) higher temperature. The weight per unit volume will stay constant enough for most uses.
    A simple way to purify a large quantity of borax at the expense of a smaller amount is to make a concentrated solution in boiling water, allow it to crystallize at a temperature below that desirable for keeping, and decant the clear liquid and discard it or use it for cleaning. The soluble impurities in the original borax are presumed to be uniformly distributed in the liquid, so that if, say, 90% of the liquid is removable by decantation and/or fitering, the remaining impurities will be reduced by 90%.
    656 grams of borax decahydrate are soluble in a liter of solution at 100 C. If the temperature is reduced to, say, 15 C, there will remain only 37.9 gram in the discarded solution. The remaining 618 grams of borax has been cleansed of about 90% of its original soluble impurities and is sufficient to make 16 liters of borax solution.
    When I first proposed this approach it was considered by certain of our resident chemists to be a complicated alternative to paying the money for analytical reagent grade of borax and weighing it to the milligram, even though it is well known among other chemists and for the same reason I stated above that such a degree of precision is not warranted by the uncertainty of the state of hydration of borax. Then, to top it off, I had a senior moment and recommended the use of 10 times more of my borax solution than was proper for D-76. That was seen as proof that I knew not whereof I spoke. Furthermore I made the assertion that 10 times too much borax was not as bad as it might seem. In the process of defending my assertion, I found a variation of D-76 that I may (or may not) call "serendipitol". Serendipity is exemplified by the fellow who accidentally walked barefoot through a certain kind of animal excrement and discovered it to be an excellent cure of athlete's foot. I seem to remember that the animal was of the male bovine type.
    I made 3 liters of D-76, two with 10 times the prescribed amount of borax in the form of 425 ml of a 4.71% solution. To one of these were added 20 grams of boric acid crystals. The third liter was made as old-fashioned D-76, using 42.5 ml of the 4.71% borax solution. The rule of this game was to pretend I didn't know about the extra borax and treat it the same as store-bought. I shot 36 exposures of HP5+, bracketing plus and minus 1/2 stop. Any consecutive 4 frames had all three exposures. As it turned out, the nominal exposure was quite good in all three cases.
    I have three cases to show. Each one shows a low resolution scan of an 8x10 print to show its chiaroscuro and a high resolution scan of a portion of that print to show resolution and granularity. The one labeled "D-76" is Metol, 2 grams, hydroquinone,5 grams, 42.5 ml of 4.7 % purified borax solution, and demineralized water to make 1 liter. "D-76 B+" is Gadget's mistake with 425 ml of the borax solution. As cure of the resulting high contrast, I took a cue from more recent D-76 and added 20 grams of boric acid crystals per liter of the mistake and called it "D-76 BB". I used VC paper. I had the contrast turned all the way down for the D-76 B+ negative and no filtration for the other two. I set printing exposure for each print to make the whitest part of the fuzzy stuff in front of my great granddaughter's teddy bear the same.
    I got the expected high contrast from Gadget's Mistake, but grain and resolution were not seriously affected. Adding boric acid to make D-76 BB brought contrast back to near normal.
    Would there be a technical reason for making D-76 BB? Its pH is lower initially than that of traditional D-76 but its activity is nearly the same, at least on short strips. Its buffering capacity should be greater, both locally and overall, which should make a difference in the effect that different types of agitation make on gradations, but the effect may not be what one is looking for. In any case, it is another possible pictorial control.
    Gadget Gainer

  2. #11
    Ian Grant's Avatar
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    Quote Originally Posted by gainer View Post
    Very interesting. I shall have to try it. Is there a British measure of weight that makes the weights come out 1, 10, 10 and water to 1 quart or gallon?
    Yes the formula is published in metric & Imperial so it was 10grains/100grains/10oz. Interestingly the ratio of M:Q and quantity is very similar to D76b.

    Ian

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    Interesting work. Thank you for the effort and for sharing the results.

    I am curious about the concoction with 10x borax. Why would this result in increased contrast? I would not have expected this. Does the pH increase that much with the additional Borax? I would have thought (I am no chemist) that after a point additional Borax would have very little effect on pH.

    Does the addition of the 20grams of Boric acid bring the initial pH back to around 9.25?

    I have many questions about the purification process too...but...it seems completely un-necessary to me? Perhaps to you too? Would the stuff straight from the 20 Mule team box not work just as well?

    Perhaps, a direct comparison of the purified to the non-purified is in order? Or, even, between reagent grade and straight 20 Mule Team?

    Thanks again for publishing.

  4. #13
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    I there are two aspects of pH. Two developers may have the same initial pH, but one may have a greater resistance to change of pH. The reaction of silver halide to development produces the halide acid as well as metallic silver. The acid then acts to reduce the local pH of the solution, more where the exposure was greater. The reduction of pH thus reduces the local activity of the developer. That is what we count on in stand or semi-stand development to produce "compensation", allowing density to build up in shadow areas at a somewhat greater relative rate than in the highlights. The initial effect of the boric acid I added was to bring the initial pH to around 8.6, but also to reduce the local dynamic change of pH.
    Gadget Gainer

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    interesting....I cannot pretend to comprehend all of this, but it is very interesting.

    I'm unclear about one thing though, if the increased contrast is expected (at least partially) due to the solution's greatly increased buffering capacity, would we not also expect increased contrast in the solution with both borax and boric acid? That is to say, wouldn't the solution with the excess borax and boric acid also have much greater buffering capacity than the nominal...and therefore also exhibit less (localized?) compensating effect?

    Clearly, it is complex.

  6. #15
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    Quote Originally Posted by gainer View Post
    PS: Reminds me of the old bawdy joke about the marriage between the circus midget and the lady giant:"Nose to nose his toes were in it and toes to toes, his nose was in it." That's about how it would be with highlights and shadows of that negative without very low contrast paper. No joy.
    I decided to illustrate my bawdy joke. These two prints were made to show what happens when I use the same printing contrast, same negative, but printing one for the highs and thr other for the lows. Development of the negative was with 10X borax timed as for ordinary D-76.
    Attached Thumbnails Attached Thumbnails nose to nose.jpg   toes to toes.jpg  
    Gadget Gainer

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    gainer's Avatar
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    Quote Originally Posted by BradS View Post
    interesting....I cannot pretend to comprehend all of this, but it is very interesting.

    I'm unclear about one thing though, if the increased contrast is expected (at least partially) due to the solution's greatly increased buffering capacity, would we not also expect increased contrast in the solution with both borax and boric acid? That is to say, wouldn't the solution with the excess borax and boric acid also have much greater buffering capacity than the nominal...and therefore also exhibit less (localized?) compensating effect?

    Clearly, it is complex.
    That might have happened were it not for the lower initial and therefore lower average pH.
    Gadget Gainer

  8. #17
    Murray Kelly's Avatar
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    It is also 1:1:10:10:2000 if one assumes an Imperial gallon is 4.6l - in fact 4.546 litres.
    Murray

    Quote Originally Posted by gainer View Post
    Very interesting. I shall have to try it. Is there a British measure of weight that makes the weights come out 1, 10, 10 and water to 1 quart or gallon?

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    Ian Grant's Avatar
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    Quote Originally Posted by Murray Kelly View Post
    It is also 1:1:10:10:2000 if one assumes an Imperial gallon is 4.6l - in fact 4.546 litres.
    Murray

    Somethings wrong with your maths Murray

    2.3:2.3:23:23:1000 works out as 1:1:10:10:434.78

    Ian

  10. #19
    Murray Kelly's Avatar
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    Sorry - quite right, Ian. I was confusing the 2 formulae - a silly mistake.
    A 'seniors' moment.:rolleyes: That .78ml would be hard to measure, but.
    Murray

    Quote Originally Posted by Ian Grant View Post
    Somethings wrong with your maths Murray

    2.3:2.3:23:23:1000 works out as 1:1:10:10:434.78

    Ian

  11. #20
    gainer's Avatar
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    Quote Originally Posted by Ian Grant View Post
    Yes the formula is published in metric & Imperial so it was 10grains/100grains/10oz. Interestingly the ratio of M:Q and quantity is very similar to D76b.

    Ian
    I tried it last night and I think I'm going to like it after I learn it. 8 minutes @ 65 F gave higher contrast than I usually look for, but a simple change of paper grade was all it needed
    Gadget Gainer

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