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<DIV><FONT face=Arial size=2>Gene,</FONT></DIV>
<DIV><FONT face=Arial size=2> We bought an expensive dial type
hygrometer with a calibration certificate from Germany, we also have less
expensive digital ones that we bought from Radio Shack both give RH and
Temperature. I have found that they are all within a few percentage points
of each other in accuracy, however, I admit I don't know which one is more
accurate, the expensive one or the el-cheapos, but their close to each other.
</FONT></DIV>
<DIV><FONT face=Arial size=2> We are drying down keyboard
blanks and have found that it takes a bit of time for the wood to
acclimate to the shop before it falls in line with the EMC
graph. When we buy the wood, the seller claims it was dried down to 8% MC
and it may have been, but after sitting in an unheated, outdoor building
for however long, it picks up moisture again. </FONT></DIV>
<DIV><FONT face=Arial size=2> If I understand what
your saying in your post, your calculating the MC with the RH (via a
Hygrometer) and weighted samples. In my opinion you need a moisture meter, We
use one that is accurate down to 5% MC, I don't know what MC you want to
attain, but 5% is pretty low. We keep our shop at 35-40% RH and 66-70
degrees year round in an attempt to be as stable as possible. When our wood has
acclimated for a while, the actual MC and EMC (via the chart) are close, but
never the same. I admit we have never tried the oven-drying method for
determining MC buy the weight, but have oven-dried wood for
determining shrinkage based on MC.</FONT></DIV>
<DIV><FONT face=Arial size=2> For our purposes we don't need
the MC as low as the Bellymen requires so we find that a moisture
meter with it's range of accuracy is well within acceptable
limits.</FONT></DIV>
<DIV><FONT face=Arial size=2> Hoadley is great and easy
reading, if you want a supplement to that look at the website for the U.S
Department of Agriculture, Forest Service they have excellent books on this type
of stuff that you can download as a PDF for free. </FONT></DIV>
<DIV><FONT face=Arial size=2> I have to ask where are you that
you need a humidifier to get the RH up to 40%? We need <U>DE</U>humidifiers to
get the RH to 40% and you can tolerate a temperature of 95 degrees
F?</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Blackstone Valley piano<BR>Michael A. Morvan<BR>76
Sutton Street<BR>Uxbridge, Ma 01569<BR>(508) 278-9762<BR><A
href="http://www.pianoandorgankeys.com">www.pianoandorgankeys.com</A><BR><A
href="http://www.thepianorebuilders.com">www.thepianorebuilders.com</A></FONT></DIV>
<DIV><FONT face=Arial size=2> </FONT></DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=nelsong@intune88.com href="mailto:nelsong@intune88.com">Gene
Nelson</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=pianotech@ptg.org
href="mailto:pianotech@ptg.org">Pianotech List</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Saturday, August 16, 2008 11:53
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> help a beginner measure mc in
wood with confidence</DIV>
<DIV><BR></DIV>
<DIV><FONT face=Arial size=2>I have been using the technique Bruce Hoadley
talks about - cut several samples of spruce (similar dimensions) to the same
weight - 100g is easy to deal with - oven dry one of them to get a dry weight
to compare the others with. Sounds straight forward enough.</FONT></DIV>
<DIV><FONT face=Arial size=2>Then I compare calculated mc using weighed
samples with my hygrometer and the EMC charts and the disagreement
begins.</FONT></DIV>
<DIV><FONT face=Arial size=2>If conditions are changing, certainly there is a
lag time for equalization but the disagreement continues. Also the samples
must be placed in the shop so they are representative - still the disagreement
continues.</FONT></DIV>
<DIV><FONT face=Arial size=2>Probably it would pay to get a much more accurate
hygrometer? </FONT></DIV>
<DIV><FONT face=Arial size=2>Is the weighing technique really accurate? How
would you determine if it was?</FONT></DIV>
<DIV><FONT face=Arial size=2>Would it be helpful to add a moisture meter to
the lot?</FONT></DIV>
<DIV><FONT face=Arial size=2>I am curious how shop folks gain confidence in
their technique to measure mc so that if the measurements are telling you the
mc is 7% it really is 7% +/- an irrelevant amount?</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I can give one example: I use my humidifier
to get the rh up to 40% at 95 deg f - this should get my weighed samples up to
about 7%rh but they insist on weighing in at 6.1%. Is this a typical
discrepancy between cheap hygrometer and weighed samples?</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Thanks for any comments. </FONT></DIV>
<DIV><FONT face=Arial size=2>Gene Nelson</FONT></DIV>
<DIV><FONT face=Arial size=2>Thanks,</FONT></DIV>
<DIV><FONT face=Arial size=2>Gene Nelson</FONT></DIV></BLOCKQUOTE></BODY></HTML>