General Information:
Dry chemicals must be accurately weighed in order to assure reliable and repeatable results.  The accuracy depends of the sensitivity of the process to that particular aspect and the amount being prepared.  The two procedures outlined below deal with small amounts (such as coating solutions) and large amounts (such as developers).

A scale capable of measuring .01 grams should be used for coating materials since the quantities are typically in the 1 - 10 gram range.  This should allow for a accuracy of 1% or better.

The scale should have the ability to compensate for a large tare (the weight of an empty bottle). A good choice is the Ohaus Centogram balance scale.

Note:  If one has a choice of a powder or a crystal, they should consider using the
           crystal as this will be less likely to get into the air and blow around the room.

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PROCEDURE FOR WEIGHING COATING CHEMICALS:

The first time (optional):

Balance the scale (empty, zero reading)

Weigh the empty dropper bottle (complete with cap and dropper) and record as its weight.  This information may be convenient if the weight of the contents needs to be measured later.

In every case:

Place a small funnel into the top of a dropper bottle.

Set the bottle with funnel onto the scale platform.

Balance the scale by adjusting its weights.  (This is the tare weight.)

Adjust the scale weights to add the weight to be measured minus one gram.

Scoop the dry chemical from its container with a CLEAN plastic spatula or spoon .

Add the chemical to the bottle until the balance just swings over.

Adjust the scale weights to add the one gram left out earlier.

Add more chemical slowly until balanced, by tapping the spatula or spoon with a finger.

Note: Be careful not to not go past the balance point because the chemical
           should not be returned to the stock bottle from the dropper bottle.  If
           extra is to be removed, treat it as a spill (see below).  Also be careful
           and add slowly, if this is an additional chemical to that already
           measured.  The order of weighing and mixing the stock solutions
           should be followed as stated in this guide since the chemicals added
           last are the least likely to cause a problem if a bit too much is added.
Note: Most scales give a more accurate measurement when they are
           moving slightly back and forth around the balance mark.

Return any chemical remaining on the spatula or spoon to its original container.

Tap the funnel to make sure all material has been delivered into the bottle.

At this point one is ready to add the appropriate amount of another dry chemical or water.

SPILLS:
Do not return or use any chemical that has spilt.  It may be contaminated and ruin the entire supply.  If a large amount is spilt or valuable material is spilt, it can be placed into a separate storage bottle, labeled, and used to make a solution.  This solution should be tested first to see if it works all right, otherwise dispose of properly or recycle to a manufacturer.  Do not mix this solution with normal stock solutions.

NOTE: The platinum palladium process is an extremely sensitive process.
               Any contamination should be avoided.

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PROCEDURE FOR WEIGHING DEVELOPER CHEMICALS:

• Place a cup (plastic or glass) large enough to contain the chemical onto the scale platform.
• Balance the scale by adjusting its weights.  (This is the tare weight.)
• Adjust the scale weights to add the weight to be measured minus one gram.
• Scoop the dry chemical from its container with a CLEAN plastic spatula or spoon .
• Add the chemical to the cup until the balance just swings over.
• Adjust the scale weights to add the one gram left out earlier.
• Add more chemical slowly until balanced, by tapping the spatula or spoon on the handle with a finger.
• At this point one is ready to pour the chemical from the cup into a large mouth bottle and add the appropriate amount of water.

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