<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; charset=iso-8859-1"> <META content="MSHTML 6.00.6000.16705" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#ffffff> <DIV><FONT face=Arial size=2></FONT> </DIV> <BLOCKQUOTE dir=ltr style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px"> <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></FONT> </DIV> <DIV><FONT face=Arial size=2><Probably an average of all meters would then be close enough?</FONT></DIV> <DIV><FONT face=Arial size=2>  </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></FONT> </DIV> <DIV><FONT face=Arial size=2><Yes, I use a cheap hygrometer with temperature and refer to the EMC chart and compare this to the weighted samples - so far I am unable to establish uniformity in measuring %mc but there is a corelation.</FONT></DIV> <DIV><FONT face=Arial size=2></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></FONT> </DIV> <DIV><FONT face=Arial size=2>< Thanks, I do visit the U.S. DOA  site frequently.</FONT></DIV> <DIV><FONT face=Arial size=2></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><Northern California foothills - east of Sacramento. Hot and dry - outside can get up to 105 F -sometimes higher - with rh in the lo-twenties to teens.</FONT></DIV> <DIV><FONT face=Arial size=2>My shop is something that my wife calls her garage. I have a swamp box that helps keep the temperature down a bit and the rh up so things don't dry out too much.</FONT></DIV> <DIV><FONT face=Arial size=2>When I need to address things like setting bearing or measuring crown is when I need control of the mc in the wood accurately. Do not have a hot box set up yet.</FONT></DIV> <DIV><FONT face=Arial size=2>When I dry my panels down I do it with the panel on sawhorses, covered with blankets and an oil filled space heater underneath. The weighted samples are in there with the panel. I only dry down to 6%-6.5% mc. However, if the shop swamp box is left off, the wood will get below that without any help so dry down strategy changes depending on the time of year and what else is in the shop - winters are relatively mild around 30-40f and 45-70%rh.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>Gene</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> <BLOCKQUOTE dir=ltr style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px"> <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></BLOCKQUOTE></BODY></HTML>