Figure 2. — Reindeer lichen sample 

 and micros aale transducer. 

 Sample was placed on aliminwn 

 foil sheet in 2- by 4- inch 

 weighing basket. 



was dropped from 90 to 20 percent. Samples were continuously weighed on microscale 

 transducers (fig. 2). Timelags for the five drying periods were determined from 

 adsorption and desorption weight-change traces.^ 



The adsorption and desorption equilibrium moisture contents of reindeer lichen 

 were determined in a controlled temperature cabinet. Six salt solutions were used 

 to establish varying levels of relative humidity. Temperature was held constant at 

 80°F. and humidity was varied between 7 and 88 percent. Samples were weighed contin- 

 uously. When equilibrium was reached at each humidity level, several samples were 

 withdrawn from the cabinet and their moisture contents measured in a vacuum oven at 

 122°F. for 24 hours. ^ Dew point was monitored in the equilibrium moisture content 

 cabinet using a Cambridge dew hygrometer. 



RESULTS 



In a given timelag period, response times varied considerably among replicates, 

 especially during adsorption tests (table 1). Nor are we the first to observe varia- 

 bility within a given timelag; Kubler,'* for instance, reported that the response 

 times of equal-sized wood samples of the same species vary by one order of magnitude. 

 Also of interest are the variations in response times we recorded for the five time- 

 lag periods (fig. 3). Our studies of reindeer lichen showed that timelag increases 



^Drying periods were defined by the following percentages of moisture change be- 

 tween initial and equilibrium moisture content: 63.3, 86.5, 95.0, 98.1, and 99.3. 



^Vacuum drying at 122°F. was comparable to regular ovendrying at 221°F. 



'*H. Kubler. Studien liber die Holz Feuchtebewegung . Holz als Roh-und Werkstoff. 

 15: 453-468. 1957. 



2 



