>This may seem like a flame, and it is not meant to be so. However, if you >have had your recording hygrothermograph recalibrated (and which springs >replaced...?) after 4 years of use, you have 3+ years worth of less than >accurate records. > >Recording hygrothermographs use a hair bundle (or sets of hair bundles) to >respond to changes in %RH (temperature is recorded from bi-metalic strips >and they tend to be very accurate) and major changes in relative humidity >(winter=cold & dry; summer=warm & wet, etc.) in combination with acids and >bases absorbed from the atmosphere (creating deliquescent salts) throw the >hair bundles out of calibration. > >Hygrothermographs should be recalibrated after any significant change in >the weather, otherwise their readings may not be dependable. > >It is largely for that reason that I began using data loggers nearly 10 >years ago; they are less likely to go out of calibration as the weather >changes, and if the readings begin to drift, it is relatively easy to plug >new numbers into the software to compensate for change. > >Jack C. Thompson >Thompson Conservation Lab >Portland, OR > Please share the brand name of your data loggers and place of purchase. Thank you. Kristi Alexander Mgr. Collections McClung Museum >http://www.teleport.com/~tcl/index.html > > >On Fri, 24 May 1996, Indianapolis Art Center wrote: > >> I use Abbeon Cal papers and pens--have had no trouble. In fact, they just >> had to replace the springs (after 4 yrs of use) for my 2 and recalibrate >> them, and they only charged me $10 each plus shipping. >> >> I don't have their number handy, but if you have access to an 800 directory >> you can probably find them. >> >> Julia Moore >> Indianapolis Art Center >> > >