The negative should be first well hardened in

Formalin......................................................

1/2 oz

Water................................

8 ozs.

and then rinsed and put into the following dilute hydrofluoric acid:

Hydrofluouric Acid......................................

25 drops

Water ..............................

5 ozs.

Do not measure the drops, but count them into a waxen or leaden dish and add the water immediately, being careful not to inhale the fumes. Almost immediately the film will be loosened, and in about a minute it may be pushed at the edges of the glass with a match and gradually slid off the glass. Transfer it immediately to the following solution:

Wood Alcohol.........................................

3 ozs.

Formalin...................................................

6 drs.

Water........................................................

4 1/2 ozs.

Again rinse and float onto a piece of clean glass and allow to dry. Care must be exercised in handling the film, not to stretch it out of shape.