The Celloidin Method 79 



Infiltration in celloidin consists ot transferring the previously 

 killed and dehydrated tissues into a dilute solution of celloidin, con- 

 centrating the celloidin, and finally molding the thickened celloidin 

 into blocks containing the material. Concentrating the matrix may be 

 accomplished by one of the following processes or by combinations 

 of processes. 



1. Transfer the tissues thorugh a graded series of celloidin solu- 

 tions of increasing concentration. 



2. Add chips of dry celloidin at intervals to the initial 2% solution. 



3. E\aporate the solvent from a large ^•olume of a 2% solution. 



METHOD 1 



Transfer the dehydrated tissues from the dehydrant into the 

 solvent. After one to several hr., transfer to 2% celloidin, covering 

 the material with at least five times its volume of celloidin. Fasten 

 a dry, rolled cork into the bottle by means of wire loops (Fig. 8.1 A, 

 B) . Put the bottle into the 53°C. oven. 



The interval in the oven varies widely. For sections of twigs 

 having a diameter of 3 to 5 mm., 24 hr. in 2% celloidin may be 

 enough. For larger pieces and for dense materials increase the time 

 to 2 days or more. After the interval in 2% celloidin, cool the bottle, 

 remove the stopper, and pour the celloidin into a dry pan (not into 

 the sink!) . Keep away from flames or sparks. Cover the tissues im- 

 mediately with 4% celloidin. Reseal the bottle, and repeat the interval 

 under pressure in the oven. Repeat this operation with 6, 8, and 

 10% celloidin. Following the last treatment, continue to thicken the 

 celloidin by adding a chip of dry celloidin every 24 hr. When the 

 celloidin is so thick that it just flows at room temperature, the mate- 

 rial is ready to be hardened as described on page 81. To determine 

 whether the consistency of the celloidin is correct for blocking, dip 

 a thoroughly dried matchstick into the celloidin, lift out a mass of 

 celloidin, and immerse in chloroform for 1 hr. The celloidin should 

 become hardened into a clear, firm mass that can be sliced easily 

 with a razor blade. A comparison of samples taken during successive 

 stages of infiltration will show the progressive increase in firmness and 

 improved cutting properties. 



METHOD 2 



The material is first given at least 48 hr. in 2% celloidin in a 

 sealed bottle in the oven. At intervals of several days the bottle is 

 cooled and unsealed, a chip of dried celloidin added, and the bottle 



