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Photo Forum / Film Photography / Darkroom / March 2004Inexpensive ph meter
I'd like some assistance choosing an inexpensive, good-enough-for-photo chemistry ph meter. Anyone? -Lew If you need something really good for photo, it will not be inexpensive (dev solutions seems to require sophisticated probes). But I use (and I'm happy with) a Hanna Checker that goes for $25 + ship brand new at Ebay (did not check other sources). Don't forget you need a calibation kit, also. Jorge "Lew" <lew@clsystems.com> wrote in news:e4udnb7ZcNkoRKLdRWPC- g@speakeasy.net: > I'd like some assistance choosing an inexpensive, good-enough-for-photo > chemistry ph meter. Anyone? > -Lew You can contact Hanna Instruments, Providence, Rhode Island, through their web site. I also use their pH Checker. Francis A. Miniter >If you need something really good for photo, it will not be inexpensive >(dev solutions seems to require sophisticated probes). [quoted text clipped - 13 lines] >>chemistry ph meter. Anyone? >>-Lew How often do you calibrate it? Does it come with a probe? -Lew Hi Lew, The probe is part of it. It is all very compact and can be put in your pocket. The probe end of it screws off so it can be replaced if it fails. As to calibration, you get three solutions (these are extra). One is pH 10; another, pH 4; the third is maintenance solution. There are two adjustsing screws at the top. Using the known pH solutions you adjust until the readings are correct. Francis A. Miniter >How often do you calibrate it? Does it come with a probe? >-Lew >The probe is part of it. It is all very compact and can be put in your >pocket. The probe end of it screws off so it can be replaced if it fails. Or gets ionized to the point that it is not producing good readings. I once measured a 5% solution of sodium hydroxide and immediately fried the meter. I thought that soaking it in glacial acetic acid word undo the damage but alas it was destroyed. Regards, John S. Douglas, Photographer - http://www.darkroompro.com Please remove the "_" when replying via email There is some info at Ryuji Suzuki's web site. http://silvergrain.org/Photo-Tech/pH.html Ouch! > Ouch! Don't panic just yet. I've been using a Hanna pHep meter with good repeatability. Actually I'm shopping for a meter with remote probe. There are some on eBay for under $70 IIRC. I think Mr. R. Suzuki is not telling us the whole story. He may be talking only of units which have a resolution of .01 of even .001. I think .1 accurate enough although .01 would be OK. I can't say for sure, but I think he may be overboard on this one. Smack dab on home base is closer than I need be. Dan My reading of Ryuji's article is that the probe will go bust if one uses it to measure developers. I have not measured this many times, but up to today mine is holding. Jorge dan.c.quinn@att.net (Dan Quinn) wrote in news:b379902d.0402281409.22fd105 @posting.google.com: >> Ouch! > [quoted text clipped - 6 lines] > I can't say for sure, but I think he may be overboard on this one. > Smack dab on home base is closer than I need be. Dan The simplest is to use pH paper calibrated in 1/2 units. >> Ouch! > [quoted text clipped - 6 lines] > I can't say for sure, but I think he may be overboard on this one. >Smack dab on home base is closer than I need be. Dan >The simplest is to use pH paper calibrated in 1/2 units. I've been following this thread and wondered why nobody. seems to use litmus paper. _________________ Ready, Fire, AIM. Bruce Brooklyn, N.Y. > I've been following this thread and wondered why nobody. seems to use litmus > paper. Cough: google: "litmus paper" Some ignorami (health food stores & co.) confuse litmus paper (red or blue strips in a corked glass vial) with pH paper, available in .5 or .1 gradations, and which comes on a spool in a nifty plastic case w/ a color- match chart. Litmus paper is paper soaked in red cabbage juice. It's good for telling baking soda from vinegar, but not much else. You may as well buy a head of red cabbage (cheaper) and after checking the pH you can make a dandy salad: Red cabbage, endive and diced fresh pears with blue cheese crumbled over the top, a French or a tomato & celery vinaigrette dressing works well. Litmus paper is not a very (not allot) accurate indication of pH. Works great in a Gilmour Chemistry Set ("Tell Mom: 41 great chemicals, including magnesium, glycerin, pot. permanganate, powdered aluminium, powdered iron ...") but not good for much else.  SignatureNicholas O. Lindan, Cleveland, Ohio nolindan@ix.netcom.com Consulting Engineer: Electronics; Informatics; Photonics. >> I've been following this thread and wondered why nobody. seems to use >litmus [quoted text clipped - 21 lines] >glycerin, pot. permanganate, powdered aluminium, powdered iron ...") but not >good for much else. Okay. _________________ Ready, Fire, AIM. Bruce Brooklyn, N.Y. > The simplest is to use pH paper calibrated in 1/2 units. Available at pool supply outlets, and at aquarium stores for 10x the price and at drugstores at 100x the price. And while at the pool store, along with ordering a pool for the summer ahead, be sure to pick up some Sodium Sulfite, Sodium Thiosulfate* and Sodium Carbonate. * Language note: standard American English is "sulfur" but standard British English is "sulphur," and New Zealand English follows the British model in this case. Similarly, standard American English is "sulfate" but standard British (and New Zealand) English is "sulphate". From http://zenvirus.com/poems/sodium-thiosulphate.html Which I found when googling for "sulfate sulphate" and where you will find, well, you will have to find out for yourself... Google first, question later. SignatureNicholas O. Lindan, Cleveland, Ohio nolindan@ix.netcom.com Consulting Engineer: Electronics; Informatics; Photonics. I have tried the pool supply route, but no one seems to stock thiosulfate anymore. Don't know why. -Lew > I have tried the pool supply route, but no one seems to stock thiosulfate > anymore. Don't know why. http://www.midwestpoolsupply.com/chemicals_sanitizers.htm 50 lbs: $48 + shipping. Look out for shipping $, some chemical houses will charge more for shipping 50lb of the stuff than for the stuff itself. Don't be afraid to 'special order' it from your friendly (and rapacious) pool supplier. TTTT: I use Freestyle's Arista brand Ammonium Thiosulfate rapid fix at $14/gal. Mix 1:9 for paper, about $1.40/gal. OTOH it is 1:4 for film, about $2.80/gal. This is still the best deal going, IMHO. S. Thio. fix is 250g s. thio./liter or about 2 lb/gal, yielding $2/gal. But then you need to add sulfite, metaborate/acetic acid (depending on religion) .... Additionally, Anchell/Troop indicate Kodak sez (or sed, till they closed the research dept.) S. Thio is no good for modern emulsions (film - too much iodide?) (and though they sell S. Thio. Fix by the tonne) and that A. Thio should be used instead. FWIW Kodak S. Thio fixer powder is $22 for 5 gal worth: $4.40/gallon. And Kodak Rapid Fix is $10/gal. Care to support our Great Yellow Father in his dotage? Only cost 6x more -- Oh, well, I thought not. Gee, and Kodak spends $10 million/year on management consultants BCG, McKinsey & Booz-Allen. Having done a 5-year stint at Booz, can't say I'm surprised. SignatureNicholas O. Lindan, Cleveland, Ohio nolindan@ix.netcom.com Consulting Engineer: Electronics; Informatics; Photonics. > S. Thio. fix is 250g s. thio./liter or about 2 lb/gal, yielding > $2/gal. But then you need to add sulfite, metaborate/acetic [quoted text clipped - 3 lines] > (and though they sell S. Thio. Fix by the tonne) and that A. > Thio should be used instead. S. Thio can be used very dilute and needs no additives. The ammonium ion's silver complexing capacity in the presence of iodide is nil. It is the thiosulfate ion which holds the silver. Cyanide will also complex with silver in the presence of iodide. Dan I have an almost full box of short range, 0.5 pH paper, made in Germany. I've tried it before going the cheap pH meter route. Jorge > The simplest is to use pH paper calibrated in 1/2 units. Jorge Omar <jorgeomar@ieg.com.br> wrote... > I have an almost full box of short range, 0.5 pH paper, made in Germany. > I've tried it before going the cheap pH meter route. > > Jorge Jorge, what was unsatisfactory about the pH papers? I would have expected them to be suitable and economical for occasional use. John John In the range of inerest, say from 8 to 10, it's just the tonality of the red band that becomes deeper. At least to my eyes/paper brand combo, it was very hard to see the difference between a borax and a carbonate solution, even placing two strips side by side. Jorge > Jorge Omar <jorgeomar@ieg.com.br> wrote... >> I have an almost full box of short range, 0.5 pH paper, made in [quoted text clipped - 6 lines] > > John >I'd like some assistance choosing an inexpensive, good-enough-for-photo >chemistry ph meter. Anyone? >-Lew I would review the numerous meters available on Ebay. I picked up a Barnant 707 in mint condition for $120 complete with probe, industrial case, buffers, bottles and instructions for use. It has to be at least 10 years old but it was never used. It measures to .01pH which is better than needed for photography but I like having the extra precision. Regards, John S. Douglas, Photographer - http://www.darkroompro.com Please remove the "_" when replying via email HI, I read this thread with much interest. I have a related but different question. For practical purposes in developing film and paper, what effect does the different PH chemicals have on the results. Other words, if I develop a film in developer with a PH of 7.0 how will it differ from film developed in PH of 6.0 or 8.0. I know the PH is the amount of acidity of the solution, but just never thought about this. Lauvone pH is a bit more complicated - 7 is neutral, below 7 it's acidic and above 7 it's alkali. Now, for almost all developers, the more alkali the solution is the more active the developer will be. Practical results of uping pH - shorter dev time for a given contrast or higher contrast for the same dev time, and almost always more grain. Jorge > HI, > [quoted text clipped - 8 lines] > > Lauvone > pH is a bit more complicated - 7 is neutral, below 7 it's acidic and > above 7 it's alkali. [quoted text clipped - 6 lines] > > Jorge Hey guys, Yeah pH paper is fine, however, you need someone with a good sense of colour to differenciate the subtle changes. For instance, when I was trying to make a good Carbonate/ Borax buffer to substitute for the Metaborate alkaline buffer. I asked a friend with good colour sense to try and tell associate the colour to the chart. She found it was very, very close in colour to the pH of 10 but not quite. Jordan later tested this solution to be pH 9.85 with his fancy gear that he uses. I think there is a very high rate of colour-blindness (I know I am) amongst males which probably accounts of a large % of this news-group - therefore... > Hey guys, > Yeah pH paper is fine, however, you need someone with a good sense of [quoted text clipped - 7 lines] > amongst males which probably accounts of a large % of this news-group > - therefore... Hum, I suppose your female friend is in her 20's, right? Now I only have to convince my wife I need a young female assistent to read pH paper color... (-: Jorge it depends, it is critical in BW developer of E6 process. it is critical in d76 due to lack of restrainer (KBr). Color developers are less critical, with changes going in yellow-blue direction, depending on pH. All developers are sensitive to pH, the higher the more active the developer is. Then each developing substance react differently to changes of pH. Atomal may work in pH 7, but developer with hydroquinone will need 10, etc. For all practical purposes - keep pH according to the manufacturer's specification. >HI, > [quoted text clipped - 7 lines] > >Lauvone >> For all practical purposes - keep pH according to the manufacturer's specification.<< Best advice I've seen yet on these responses. Each developer formulation is designed for a specific level of activity based on the amount and specific developing agents used, amount of sulfite, and bromide, etc. Playing with the pH will not only shift the activity, but may also change grain, shadow detail, contrast, etc. In other words, if you like what you get from a certain developer, pH is something you DO NOT want to play with. Someone mentioned it being important in E-6 first developer, but the color developer is much more critical and pH changes will cause color shifts. It is so critical that processors are advised to make minor pH adjustments based on the sensitometric results of specially exposed control strips, because their expensive $1000 meters are not sensitive or accurate enough to adjust based on the actual pH reading. These labs pay more for a special electrode than the $50 hand held pH meters everyone is so ready to rely on. Bernie >Someone mentioned it being important in E-6 first developer, but the color >developer is much more critical and pH changes will cause color shifts. incorrect, consult any E6, or equivalent, manual. FD is CRITICAL for speed and color. CD has little effect on speed, but will affect color. You are right, it requires pH adjustment, usually adding NaOH or KOH solution. All the details are in E6/AP44 process manual. > It is >so critical that processors are advised to make minor pH adjustments based on >the sensitometric results of specially exposed control strips, because their >expensive $1000 meters are not sensitive or accurate enough to adjust based on >the actual pH reading. it is possible to determine all components of FD and selectively adjust the tank solution. It requires knowledge, good lab and access to components. It is done in large labs running E7 or in motion picture industry. incorrect, you can measure pH with accuracy 0.001 unit, nothing special (unit and an electrode). Except you won't find standard buffers accurate to +-0.001. It has to be done in-house, and it is quite challenging. What is important is the final result. You run your test strip and take readouts, you plot them. On that result, you determine all necessary changes, replenishment rate, changing of pH. It is however qualified answer - because you need good prints, or slides not good test strips. If your E6 films are OK and test strips not, just keep your process stable with test results "off". Your customer doesn't give .... as long as films are OK. Test strips are made of one particular film brand/type and they react differently to other brands or types from the same manufacturer. >These labs pay more for a special electrode than the $50 >hand held pH meters everyone is so ready to rely on. Yes, a research grade pH electrode is expensive, even several hundreds of dollars. You get what you pay for. Very important while measuring solutions with high ph (>10)and high sodium content. >Bernie jazztptman wrote >>Someone mentioned it being important in E-6 first developer, but the color developer is much more critical and pH changes will cause color shifts.<< friend responded >>>incorrect, consult any E6, or equivalent, manual. FD is CRITICAL for speed and color. CD has little effect on speed, but will affect color. You are right, it requires pH adjustment, usually adding NaOH or KOH solution. All the details are in E6/AP44 process manual.>>> Friend, if ph is so critical in the FD, then why does the Kodak Q-lab system have labs test the bromide level of FD to verify proper replenishment, instead of just checking pH ? Yes, severe FD problems can cause color shifts, but it basically controls density, where the CD as you stated will cause color shifts and needs to be adjusted for pH. Bernie >Friend, if ph is so critical in the FD, then why does the Kodak Q-lab system >have labs test the bromide level of FD to verify proper replenishment, instead >of just checking pH ? Because concentration of bromides has bigger efect than pH. Bromide is a major component of starter part. If mixed with a replenisher in wrong proportion, it will lead to unacceptable results. pH of FD should be within 0.05. Even 0.1 difference is acceptable, with minimal color shift and changes in speed within limits. In CD differences in pH of 0.1 have similar effect to variations of pH in FD, but it get really bad if you vary +-0.3 unit. Then you have big color shift. But you should never have CD with pH variation larger than 0.1 from desired value. Any manual will tell you that FD is the most critical. Time, agitation, temperature, replenishment, pH, contamination all have tightest requirements. Replenishment is not only about pH but about keeping composition at constant level. Bromides are important and easy to monitor. Bromides variation can be due to replenishment or use of different films. pH and bromides do not test the same property, they complement each other. friend® wrote: > it depends, it is critical in BW developer of E6 process. it is > critical in d76 due to lack of restrainer (KBr). Color developers are [quoted text clipped - 6 lines] > For all practical purposes - keep pH according to the manufacturer's > specification. Some developers containing metol and hydroquinone have a pH less than 10. In this case the hydroquinone does not act as a developer but acts to reconstitute the used up metol. >Some developers containing metol and hydroquinone have a pH less than 10. In >this case the hydroquinone does not act as a developer but acts to >reconstitute the used up metol. The activity level of hydroquinone is diminished below 10pH but that is not to say that it does not develop the halide. It just doesn't have enough energy to initiate the halide reduction on it's own. Regards, John S. Douglas, Photographer - http://www.darkroompro.com Please remove the "_" when replying via email In my experience, very fine pH gradations are usually not critical in B&W developers. I've played around for years concocting my own formulas and/or modifying Patrick Gainer's concoctions. What I've discovered is that there can be a major difference in developer activity between pH 8 and pH 10, for example, but not as much between pH 9 and pH 10. For practical purposes, pH papers are fine for testing, always providing you're not color-blind. I have two rolls of pH papers--one that gives results for whole numbers, e.g. 5, 6, 7. . . and one that gives intermediate numbers, eg. 7.5, 8.5, etc. By the way, in a recent issue of Photo Techniques, Gainer experimented with adding Hydroquinone to his Phenidone-Vitamin C concoctions to test the superadditivity effect. Since I've been using a variant of that for years to develop Delta 400, I followed his suggested formula which called for 1 tsp. Borax. When I tried it at his suggested starting time, the negs were underdeveloped by at least two full stops. I tested the pH with my paper, and discovered that it was somewhere between 8 and 9. So I added 1/2 tsp. Kodalk Balanced Alkali and the negs came out beautifully with no appreciable increase in grain. With the addition of the Kodalk, the pH tested out to approximately 10. >> Some developers containing metol and hydroquinone have a pH less than >> 10. In [quoted text clipped - 10 lines] > John S. Douglas, Photographer - http://www.darkroompro.com > Please remove the "_" when replying via email SignatureUsing M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/ >I read this thread with much interest. I have a related but different >question. For practical purposes in developing film and paper, what effect >does the different PH chemicals have on the results. Increasing the pH will increased contrast, increase granularity, produce a higher level of grain migration (degrades sharpness) and soften the emulsion a little more than normal. Should you want to see the results of developing using a high-pH developer, I suggest developing TMX-100 in HC110 and use a low pH developer such as D-23 or Microdol-X. Regards, John S. Douglas, Photographer - http://www.darkroompro.com Please remove the "_" when replying via email > I'd like some assistance choosing an inexpensive, good-enough-for-photo > chemistry ph meter. Anyone? > -Lew There are liquid indicators. A very small dropping bottle of it came with my ph 4, 7, and 10 standards. Indicator solutions may be a good way to go. In fact I think I'll do a little shoping myself. pHydrion might be a good place to start. Dan >> I'd like some assistance choosing an inexpensive, good-enough-for-photo >> chemistry ph meter. Anyone? [quoted text clipped - 4 lines] >good way to go. In fact I think I'll do a little shoping myself. >pHydrion might be a good place to start. Dan standard pH buffers may be colored, but it does not mean, they act as an indicator. For all practical purposes-pH indicators, liquid or as papers, are useless in photography. If you want pH meter, contact any laboratory supplier. I don't have all the catalogs at home, just Sigma Aldrich. Cheap one between 70 and 100 dollars- Corning Chek-Mite pH tester models pH-15, -20, -25, accuracy +-0.04, 1 or 2 point calibration, replaceable epoxy electrode, if you have 190-200 dollars, you get pHTester 3 with double junction electrode, accuracy +-0.01 in range of 0.00-14.99, push button calibration with buffers of 4.01, 7.00, 10.00. more expensive model comes with a temperature probe and automaticaly adjusts pH reading. It should be sufficient. For extra 100 you get even better unit, for 500+ you get research grade instrument. You'll need to read about care of pH electrodes, otherwise, you'll have to buy them too often. In general they have to be stored in saturated potassium chloride solution, never left to dry. If it's dried soak in water for few days, it may react slowly. Do not touch with your fingers the sensing bulb, otherwise needs soaking in diluted HCl, then in water (to remove poteins). Your supplier should have an info about maintenance, care. Friend: Why are indicator papers useless in photography? I have a source for test papers with half step accuracy from 1.0 through 10. -Lew > Friend: > Why are indicator papers useless in photography? I have a source > for test papers with half step accuracy from 1.0 through 10. Lew The ph values I read for working strength solutions run from neutral to eleven. For my purpose, values for other strength solutions or acidic developing agent solutions, are more of an academic interest. I've not measured a value of less than ph 6.8 and that for a very dilute, only sodium thiosulfate fixer. I use fixer very dilute, one-shot. Half step ph accuracy is not enough. Half step accuracy is not at all accurate. Actually I think paper or solution indicators can be read closer than that. My pHep meter has a resolution of .1 ph. That in my opinion is close enough. The matter of takeing ph measurments is largly academic. Why in the world go to the trouble? Why are you interested in ph measurements? You think you are going to learn something, right? Dan > The matter of takeing ph measurments is largly academic. Why in > the world go to the trouble? Why are you interested in ph > measurements? You think you are going to learn > something, right? Dan It's academic for those of us using chemicals one shot but how about those who top up chemicals? Nick > It's academic for those of us using chemicals one shot but how about those >who top up chemicals? I'm not so certain that it's even academic for one shot if one is using something other than "photo grade" materials. How many of us are using 20 Mule Team Borax ? Arm-&-Hammer Washing Soda ? Red Devil Lye ? And IMO if one is experimenting with any ascorbate developers, the least you should do is to plot the pH. Regards, John S. Douglas, Photographer - http://www.darkroompro.com Please remove the "_" when replying via email > I'm not so certain that it's even academic for one shot if one > is using something other than "photo grade" materials. How many of us > are using 20 Mule Team Borax ? Arm-&-Hammer Washing Soda ? Red Devil > Lye ? Importantly ph measurements of a least .1 accuracy can help identify which variable or variables are involved when processing results are other than expected. When new chemistry is brought into stock for homebrewers or for ready-mix, the ph of it's solutions should be checked. In a systematic way working strength solutions made up from stock or concentrate solutions should be checked. I've recorded the date brought into stock and source of my store of chemicals. I've practiced some the above recommendation. "...if one is experimenting with any ascorbate developers..." I turned out another very pale yellow image of a step-wedge two days ago. On a sheet of 5x7 Arista grade 2 RC paper I used .0625 gr. ascorbic acid and 1.5 gr. sodium carbonate monohydrate; all that in 125ml of water with 8 minutes in the developer. I think that Vit. C is not a developing agent. At the very least it should not be listed as a "developing agent". I think it belongs within another group of chemicals; chemicals which influence the developing process in some manner or another. I did find one film developer formula which used Vit. C only: one tsp Vit. C and two tbl. of "washing soda". Develop thirty minutes. Other than that I don't recall any C developers which contained no other agent. Metol, hydroqinone, p-aminophenol, and you know of others which will stand on their own. BTW, is sodium ascorbate as alkaline as sodium sulfite. How about D23-VC!! Dan > I did find one film developer formula which used Vit. C only: one > tsp Vit. C and two tbl. of "washing soda". Develop thirty minutes. That should read: Develop eight minutes. > Other than that I don't recall any C developers which contain > no other agent. Metol, hydroqinone, p-aminophenol, and you > know of others which will stand on their own. At www.pofig.com I did find another formula, one from Russia. > BTW, is sodium ascorbate as alkaline as sodium sulfite. How about > D23-VC!! D23-VC would be the usuall D23 but with 100 grams of sodium ascorbate substituteing for the sulfite. Dan > BTW, is sodium ascorbate as alkaline as sodium sulfite. How about >D23-VC!! Dan Sacrilege ! Heresy ! And besides, it won't work. Regards, John S. Douglas, Photographer - http://www.darkroompro.com Please remove the "_" when replying via email By the way, did anybody come up with an inexpensive pH meter? _________________ Ready, Fire, AIM. Bruce Brooklyn, N.Y. >By the way, did anybody come up with an inexpensive pH meter? Yes. http://www.technika.com/Sper/s840035.htm Regards, John S. Douglas, Photographer - http://www.darkroompro.com Please remove the "_" when replying via email I paid $24 + postage for a brand new, in the blister Hanna checker from K-Mac Art and Pond Supplies in Ebay. It works, and one needs also the calibration kit. Jorge camclicker@aol.comcom (Bruce) wrote in news:20040320225939.26960.00000134 @mb-m21.aol.com: > By the way, did anybody come up with an inexpensive pH meter? > _________________ > Ready, Fire, AIM. > Bruce > Brooklyn, N.Y. > > BTW, is sodium ascorbate as alkaline as sodium sulfite. How about > >D23-VC!! Dan [quoted text clipped - 5 lines] > John S. Douglas, Photographer - http://www.darkroompro.com > Please remove the "_" when replying via email Sodium ascorbate is nearly neutral. 7.5 grams of metol will activate about 30 grams of sodium ascorbate. A touch of borax might cause it to set fire to your film, if that's what is meant by burnt out highlights. I would suggest leaving out the borax and using the metol-ascorbate concoction as the first bath of a 2-bath. it is not academic. When I mix my own solutions, I check both pH and density. It lets me detect some possible mistakes. No-one is perfect. It is cheaper than ruined films. Also, when you are positive about pH and density, then you can rule out possible sources of bad results (if you get one). >> The matter of takeing ph measurments is largly academic. Why in >> the world go to the trouble? Why are you interested in ph [quoted text clipped - 5 lines] > > Nick Yeh, learning stuff is cool. -Lew when you need to measure pH +-0.05 unit, and the best from an indicating paper is 0.5, what is the use of the paper? Just enough for a stop bath, maybe fixer. Bleach and developers either need better accuracy or are colored, which will mask the color change of the indicating paper. Forget indicating papers. Even the cheapest pH checker should be better. >Friend: > Why are indicator papers useless in photography? I have a source for >test papers with half step accuracy from 1.0 through 10. >-Lew "friend®" wrote: > when you need to measure pH +-0.05 unit, and the best from an > indicating paper is 0.5, what is the use of the paper? [quoted text clipped - 7 lines] > >test papers with half step accuracy from 1.0 through 10. > >-Lew I have found that there is no direct correlation between granularity and pH. There are too many other factors involved. I have developers that give finer grain and better resolution than D-23 with no sulfite and pH above 9. Have any of you measured pH of HC110B? I don't believe it is as high as you might think. Rodinal is another one that may not be what you would think. AgX grain size is the most important factor, composition of a developer is important too. pH would be included in the developer composotion. Regarding HC and Rodinal - look at the composition after dilution. pH is high, but total alkalinity is low, buffering capicity low, total amount of developing agent low. In due course of developing active compounds are exhausted quickly, bromides increase particularly in dense areas, hence development is slowed down significantly. There is no reason to single out pH as one important factor. ------------------------------------------ >I have found that there is no direct correlation between granularity and >pH. There are too many other factors involved. I have developers that [quoted text clipped - 5 lines] > >Rodinal is another one that may not be what you would think. >Have any of you measured pH of HC110B? I don't believe it is as high as >you might think. MSDS states 8.8~9.0 for working strength solution. I would guess 9.0 for Dil. B. >Rodinal is another one that may not be what you would think. It works fine at 1:75 or higher dilutions. I've heard Dektol does nearly as well. Regards, John S. Douglas, Photographer - http://www.darkroompro.com Please remove the "_" when replying via email |
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