rapidly enough to cause boiling or a splashing explosion that may splash the solution on someone nearby. Acids should always be poured slowly into a solution (near the edge of the container) while rapidly but carefully stirring the liquid. LABELS Mixing tanks, storage tanks, and machine tanks for developer, stop bath, fixer, and other solutions must be labeled  clearly  with  waterproof  tape  or  nameplates  to reduce the chance of putting a solution into the wrong tank. The label should contain the name of the solution, the date it was mixed, and the name of the person that mixed it. It is also mandatory that hazardous chemical labels  be  attached  to  all  chemical  containers. CONTAMINATION All of the mixing equipment and the mixing area must be cleaned immediately after use to prevent solution  contamination.  The  mixing  tools  and  tanks must be thoroughly cleaned right after use to prevent dried solutions from forming encrustations that could dissolve when a new solution is mixed. Mixing tools that have  not  been  used  in  some  time  should  be  washed before use to remove any dust or dirt that may have accumulated. PREPARATION   OF   PHOTOGRAPHIC SOLUTIONS When mixing photo chemicals, you should always start with clean tools and a clean tank with the right amount of water-usually about one half to three fourths of the final volume. The temperature of the water must be as specified in the instructions. Developers are generally mixed at or about 90°F to 125°F, while fixers are mixed in water that should not be much above 80°F. Always dissolve or dilute ingredients in the order called for by the instructions. Dry ingredients must be completely dissolved before the next ingredient is added. All liquids must be completely diluted, while stirring, before the next ingredient is added. After a liquid is added to a solution, rinse the bottle and add the rinse water to the solution, so all the concentrated  liquid  is  used. After all ingredients have been combined and thoroughly dissolved, diluted, and mixed, water should be added to bring the solution up to the correct volume. Do  not  forget  to  mix  this  water  thoroughly  into  the solution. FOLLOW DIRECTIONS Before  mixing  photographic  chemicals,  you  should read the manufacturer’s directions carefully. Much research  goes  into  the  production  of  chemical  products; however, it is only effective when the chemical is mixed and used properly. The directions for even the most familiar product should be reviewed, because there are continual attempts to improve photographic materials; for example, new film or developer combinations may call  for  changes  in  dilution,  processing  time,  or temperature to get the required results. Learn to follow directions. This is very important in the preparation of chemicals for both quality and safety reasons. Remember to follow the proper procedures for chemical safety. You should prepare the chemicals in a well-lighted and well-ventilated room. Do not taste or inhale any chemical. You are required to wear rubber gloves, a rubber apron, eye protection, a long sleeve shirt, and a respirator for your personal protection. Remember,  for  safe  mixing  and  quality  results, FOLLOW  DIRECTIONS. CAUTION In most imaging facilities, it is common practice to connect a hose to the water spigot to aid in filling a chemical mixing tank and to prevent splashing in the sink. Aboard ship, hoses attached to potable water spigots can back siphon chemicals from the tank or sink into the drinking water supply. Such hoses should either be removed after each use or have a backflow preventor  installed  in  the  plumbing  system. CHANGING   PERCENTAGES You must know how to prepare percentage solutions from liquid chemicals. When the chemical on hand is in liquid form and of known strength, a percentage solution can  easily  be  prepared  by  the  following  method: Amount  Wanted  x  Strength  Desired Strength on Hand Multiply the amount wanted by the strength desired and divide the product by the strength of the chemical on hand; for example, you need 11 ounces of 28 percent acetic acid. The chemical on hand is glacial acetic acid, 99.5  percent.  Thus, 11  x  28 308 99.5 _⁼99.5= 3.09 = 3 ounces 9-9