sealed into the framework with a nonhardening 

 calking- compound that is sold under the trade 

 name of Kalk Kord by Sears, Koebuck & Co. 3 



A special roller was fabricated for preparing a 

 smooth, even layer of calking. This roller, shown 

 in figure 2, pressed the ribbons of calking material 

 into a uniform layer on which the glass could be 

 easily seated. When the pane of glass was pressed 

 against the calking, a sharp, raised area, made by 

 a notch in the roller, showed when the glass was 

 uniformly seated. This is a critical point! If 

 seating is not perfect, the chamber will leak. An- 

 other ribbon of calking was then laid on top of 

 the glass, and the angle retaining strips were fas- 

 tened with bolts to hold the glass in place. "When, 

 with time, the calking pulled away from the glass, 

 it was pressed back in place with a special tamping 

 tool, shown in figure 2, or additional calking was 

 added to renew the seal. The framework of the 

 chamber was painted inside and out with white 

 polymerizing plastic. 



Figure 3 shows details of the calking and glass 

 retainer strips for a corner installation, both top 

 and side view. Another view of a divider between 

 two panes of glass is also shown in figure 3 with 

 side and top views. The joint where the side 

 meets the top and the glazing method at that 

 point are also detailed. 



The chamber was tested for leaks by admitting 

 a charge of Freon 12 to about 10 inches of water 

 pressure, as indicated by a manometer, and by 

 checking all the surface for the presence of halogen 

 with a halogen detector. 



Door Construction 



For access to the chamber, a door, 29 inches wide 

 and 59 inches high, was constructed of aluminum 

 sheet, using two layers each 0.5-inch thick. These 

 layers of aluminum were fastened together with 

 blind screws and two windows machined out as 

 indicated in figure 4. A slot was machined around 

 each window opening, into which the glass was 

 seated. To secure the door to the chamber, 30 

 studs, 0.5 inch in diameter, were set in the door- 

 frame and the heads welded to prevent leaks. A 

 half-round groove was machined in the door, and 

 in this groove a gasket made from tygon tubing 



3 Use of this and other trade name material mentioned 

 in this publication does not constitute an endorsement 

 by the U.S. Department of Agriculture. 



WASHER 

 HARD SOLDER 



ROLLER 



CALKING TAMPER 



Figure 2. — Calking applicator and tamping tool. 



was inserted. The gasket was made continuous 

 by heat sealing it at the corners in right-angle 

 joints. In addition to the gasket, a layer of calk- 

 ing was placed on the rest of the doorframe. The 

 pressure of sealing the door extruded calking in- 

 side the doorframe, and a seal was indicated by 

 uniform expressing of the calking compound. 

 There has been no difficulty in sealing the door, 

 and it is easily removed and replaced by two men. 



Utility and Service Entrances 



The pressure-tight electrical fitting, shown in 

 figure 5, was one of the type used to introduce 

 electricity into the chamber. The channel iron 

 at the midline of the chamber was drilled and 

 tapped to receive the 14 -inch pipe thread on the 

 fitting. The fitting was made of brass except the 

 insert, which was tygon. A single No. 12 wire 

 was inserted through the hole in the tygon sleeve, 

 and the assembly secured in the body of the fitting 

 and tightened to a leakproof seal. 



Two sizes of pressure- tight refrigerant tubing 

 fittings were made according to the diagram in 

 figure 6. The connection was threaded into the 

 channel iron in the chamber, the refrigerant tube 

 inserted, and the fitting tightened on the tube and 

 sealed. Two of these units were used to install 

 14-inch and %-inch refrigerant tubing. 



Figure 7 shows details for admitting one type 

 of thermoregulator to the inside of the chamber. 



% 



