|Rotex Micro Mix Mini Lab Combo.|
Desilvers C-41 fixer and stabilizer; RA-4 bleach-fix and stabilizer; EP-2 bleach-fix and low-flow wash; E-6 fixer; black and white fixers.
Rotex Micro Mix Combo models combine the famous Rotex Micro Mix electrolytic silver recovery units with Rotex ReLoadable steel wool tailing canisters positioned on Formica stand to save floor space.
Calculating Silver Returns...
In 1987 the average independent mini lab processed an average of 61 rolls per day, or 427 rolls per week and 22,204 rolls per year. This average mini lab using RA-4 paper, would desilver 270 batches (2 1/2 gallons) (22,204 divided by 82) to recover 262 Troy Ounces (270 x 97%) electrolytically. The balance, 8 Troy Ounces, would be trapped in the steel wool canister or lost. 262 Troy Ounces may be sold for 85 to 92% of the "spot price" quoted by Handy & Harmon in most daily newspapers. At a $5.00 "spot price" the 262 Troy Ounces will return $1,113.50 to 1,205.20. A similar volume using EP-2 paper will return up to 27% more.
Process RA-4 Color Print Paper...
Note that RA-4 bleach fix has a pH value of approximately 6.5 so that it functions as a stop bath. To remove silver efficiently from RA-4 bleach fix the pH must be raised to at least 7.5 or "until ammonia fumes are released". This is most easily accomplished by adding sodium hydroxide or ammonium hydroxide. Process EP-2 typically has a pH of 8 and usually does not require adjustment unless an unusual amount of C-41 or E-6 is present in the mixture.
Black and White...
Black and white fixers may also be desilvered in Micro Mix Combos at reduced plating currents. MMC 10 and MMC 10-5 will recover 1/2 Troy OPunce per hour when set at 4 amperes plating current. MMC 25 will recover 1 1/2 Troy Ounces per hour when set at 12 amperes plating current. Rotex also offers lower cost Ultra Combos for labs that do not require color capability.
Plating current shown is the maximum recovery rate for typical mixtures of C-41 and RA-4 pr EP-2 with a pH value of 7.5 or higher. Plating capacity is sharply reduced as silver concentrations are depleted.