66 BULLETIN 1136, U. S. DEPARTMENT OF AGRICULTURE 
MEAN RELATIVE HUMIDITIES 
A study of the weather reports for various parts of the country 
shows that the average atmospheric temperature and humidity con- 
ditions vary greatly in different regions and that they also have 
important seasonal variations in each place. The mean relative 
humidities for a number of cities are presented in Table 26 to exhibit 
these variations. Unfortunately, converting mean relative humidities 
directly into equilibrium moisture content is impossible, so that the 
chief value of this table hes in the general survey it offers. 
TABLE 26.—MVean relative humidities at various points in the United States 
Mean relative humidity in per cent 
City | | 
Winter | Spring) SY" | Fan | Annual 
Cleveland, OM fe Jess. : eT eae 8 ee ie 77 72 70 | 7 7 
Menver iCOlos: 4e4 tha fake Fos eS aes Se 54 51 49 | 46 50 
DIU BFS Oa Db. ea tim se EE a ee eR 45 27 41 | 46 40 
GalvestomiWexs Soh 42 Ae Oped. ck SUES ual Sons FR: Se Tee 84 82 79 78 81 
IMiadisomisWashes 282038 oe ba 0 eee ae Cee pee 82 80 71 | 75 7 
em DHISS “NOON. = sect ae Re Semen Meee ae eee Ae = ee 74. 69 75 | 71 72 
Ne wi @ reams lie sre apo OE seca eee ee eT Eee eee eee 79 15 7 77 77 
ING Wa OE Ke WIN SY) cei bE US ee Oe Ae pie WIE Re 2a se! 73 70 74 75 73 
IPensacola, sla. i as Se eee SE een a ee 80 77 79 {65 78 
TON AV Ces Gub-ehny NI ay Auge comm steht A Siante tel eoe i lgeh yume: SNe a os hl ie eo oe 47 32 32 4] 38 
POG ULAMGAORES Mate Be iene Spee ee oe gens ee Oe 84 72 67 | 79 75 
SangDiesos Calif seret: We Oe eee a yeti eee teat eee ES 74 78 81 7 78 
SDOKAN Ee AVWAS Ht sea 5 0 2g ak Se Le aa ee eee eee aes ee 82 61 47 | 67 64 
Wilms tonveiNiy Cites = 2S ESS O Leta Sai ae Sat eee 78 7 83 81 80 
SPECIFIC FINAL MOISTURE-CONTENT VALUES 
While it is hardly possible to lay down inflexible rules for proper 
final moisture content, the information in Table 27, which is based 
on average conditions in the East and in the Middle West, may 
serve as a guide in the drying of stock for specific purposes. 
TABLE 27.—Final moisture content desired for wood for various purposes 
Final Final 
Kind of stock moisture Kind of stock moisture 
content content 
Per cent Per cent 
Wun Eun: eee. ee eee ee eR es eee 5-7 || Vehicle wheel and box parts_____------_- 
Misicalinstrumentsoe se sae se eee 5-7 || Vehicle stock, except wheel and box parts- 15-18 
interior woodwork: 212.02 asst i 2 6-8 ||| Adreraft. .- 0.2 5. 8 os ee ee 8-12 
Softwoods for long freight shipments_-___} 12 or less. || Miscellaneous outdoor material-_---_-___ 12 
GunStocks iene 2: Sas a eae eee ee 6-8 
Outdoor sporting goods (bats, golf sticks, 
tennis rackets, polo mallets, ete.)_____- 10 
STEAMING SAP GUM 
Some mills make a practice of steaming sap gum before putting it 
out in the yard to dry. Such steaming serves a double purpose. It 
sterilizes the stock, killing all fungous spores and any insects or 
larve present, and it contributes to rapid surface drying of the stock 
after the removal to the air, thus reducing the hazard of reinfection. 
