rkj155
Member
Hi All
Well I got a lesson about Vacuum and how to use it to stabilize. this comes from a person who teaches Physics at a University near me.
The way he put it is what most people call a vacuum is really a pressure.
He gave me the following paper:
Pressure terminology
Most pressure gauges (Bourdon tubes, manometers, and bellows) really measure difference in pressure between two points. They are usually arranged to measure the difference between atmospheric pressure and another pressure. The atmospheric pressure is due to the weight of the air and water vapor above the surface of the earth. Standard atmospheric pressure (or standard barometric pressure) is:
14.696 pounds/square inch (or235.1 osi)
29.92 inches of mercury column (or 760 mm Hg).
33.94 feet of water column (or 407.3†WC)
101 325 N/m2 (Newtons per square metre)
The actual atmospheric pressure varies with weather, latitude, and altitude. (About 1/2 psi (3.45 kPa) less for each 1000 feet above sea level.)
Absolute pressure is the sum of the gauge pressure and the atmospheric pressure. An absolute pressure of zero would exist only in a perfect vacuum.
Stating the previous table was measurements at sea level. The following are values of one (just above an absolute vacuum):
1 psi = 27.7†WC ,16 osi, 2.04" Hg, 6.895Kpa
1 osi (ounce/sq. in.)= 1.73WC, 0.128" Hg, 0.063 psi, 0.431 Kpa
1"Hg (mercury)= 13.6 Wc, 7.6 osi, 0.49 psi, 3.386 Kpa(0"c)
1"WC (water column)= 0.58, 0.074" Hg, 0.036 psi, 0.249 Kpa(0"C)
The only figures that I can relate to are psi and Hg (mercury)
Basically what he told me is that the only vacuum is an absolute vacuum and that it is measured by the number of molecules in a certain volume (I forget the size he said). Everything else is pressure the example he gave was:
Low pressure-----less than atmospheric pressure
0 pressure (zero pressure on our pressure pot gauge).-----atmospheric pressure or 14.696 psi.
High pressure---pressure that is more than atmospheric pressure and that is measurable on our pressure pot gauge.
How to properly use vacuum so that pressure will push the stabilizing liquid into whatever is being stabilized.
Place wood to be stabilized in your stabilizing chamber with a weight on top of the wood so it will not float when stabilizing liquid is added. Draw your vacuum to what ever level you want (lets say 28†of mercury) let it sit and draw the air out of the wood (various woods require various times, depending on it’s density). With the vacuum still on introduce the stabilizing liquid over the wood by a couple of inches and make sure that no air gets into the chamber with the stabilizing liquid. Let this sit for a while (5 to 15 minutes) then release the vacuum. Now we have gone from 28 “ Hg or approximately .97 psi to atmospheric pressure at 14.696 applying 13.72 psi to the stabilizing liquid and pushing it into the wood.. This pressure is probably enough to push the stabilizing liquid into most of our soft to medium density woods. This should take from 2 to 5 hours. Then you remove the wood from the stabilizing liquid and dry. If you are stabilizing a piece of dense hard wood you may have to apply more pressure. This can be done by placing your stabilizing container inside of your pressure chamber (pressure pot) and pressurizing to 40-60 psi for4 to 6 hours.
I use a 1 quart mason canning jar with 2 fittings on the top that take 1 quarter inch thick wall hose. One for the vacuum line the other for the stabilizing liquid. The jar will hold enough wood to make 3 to 6 pens depending on pen size.
Ron
Well I got a lesson about Vacuum and how to use it to stabilize. this comes from a person who teaches Physics at a University near me.
The way he put it is what most people call a vacuum is really a pressure.
He gave me the following paper:
Pressure terminology
Most pressure gauges (Bourdon tubes, manometers, and bellows) really measure difference in pressure between two points. They are usually arranged to measure the difference between atmospheric pressure and another pressure. The atmospheric pressure is due to the weight of the air and water vapor above the surface of the earth. Standard atmospheric pressure (or standard barometric pressure) is:
14.696 pounds/square inch (or235.1 osi)
29.92 inches of mercury column (or 760 mm Hg).
33.94 feet of water column (or 407.3†WC)
101 325 N/m2 (Newtons per square metre)
The actual atmospheric pressure varies with weather, latitude, and altitude. (About 1/2 psi (3.45 kPa) less for each 1000 feet above sea level.)
Absolute pressure is the sum of the gauge pressure and the atmospheric pressure. An absolute pressure of zero would exist only in a perfect vacuum.
Stating the previous table was measurements at sea level. The following are values of one (just above an absolute vacuum):
1 psi = 27.7†WC ,16 osi, 2.04" Hg, 6.895Kpa
1 osi (ounce/sq. in.)= 1.73WC, 0.128" Hg, 0.063 psi, 0.431 Kpa
1"Hg (mercury)= 13.6 Wc, 7.6 osi, 0.49 psi, 3.386 Kpa(0"c)
1"WC (water column)= 0.58, 0.074" Hg, 0.036 psi, 0.249 Kpa(0"C)
The only figures that I can relate to are psi and Hg (mercury)
Basically what he told me is that the only vacuum is an absolute vacuum and that it is measured by the number of molecules in a certain volume (I forget the size he said). Everything else is pressure the example he gave was:
Low pressure-----less than atmospheric pressure
0 pressure (zero pressure on our pressure pot gauge).-----atmospheric pressure or 14.696 psi.
High pressure---pressure that is more than atmospheric pressure and that is measurable on our pressure pot gauge.
How to properly use vacuum so that pressure will push the stabilizing liquid into whatever is being stabilized.
Place wood to be stabilized in your stabilizing chamber with a weight on top of the wood so it will not float when stabilizing liquid is added. Draw your vacuum to what ever level you want (lets say 28†of mercury) let it sit and draw the air out of the wood (various woods require various times, depending on it’s density). With the vacuum still on introduce the stabilizing liquid over the wood by a couple of inches and make sure that no air gets into the chamber with the stabilizing liquid. Let this sit for a while (5 to 15 minutes) then release the vacuum. Now we have gone from 28 “ Hg or approximately .97 psi to atmospheric pressure at 14.696 applying 13.72 psi to the stabilizing liquid and pushing it into the wood.. This pressure is probably enough to push the stabilizing liquid into most of our soft to medium density woods. This should take from 2 to 5 hours. Then you remove the wood from the stabilizing liquid and dry. If you are stabilizing a piece of dense hard wood you may have to apply more pressure. This can be done by placing your stabilizing container inside of your pressure chamber (pressure pot) and pressurizing to 40-60 psi for4 to 6 hours.
I use a 1 quart mason canning jar with 2 fittings on the top that take 1 quarter inch thick wall hose. One for the vacuum line the other for the stabilizing liquid. The jar will hold enough wood to make 3 to 6 pens depending on pen size.
Ron
] ). Every time, the blanks were all fully submerged after the first vac of only about 10 to 15 minutes. Also, I have a weak pump and it will only draw 20 to 22 hg.