On Sun, 25 Jan 2004 03:39:30 GMT, "Mike in Mystic"
wrote:
Tonight, when I started to work on the tablesaw and as the garage/shop
heated up (using a 80,000 BTU propane heater), I noticed that the jointer
surfaces already had signs of light rust again (pretty faint, but still
there, and after only about a week since I cleaned it, and coated it with
Topcote (no wax on the jointer)). As the room became warmer, I saw SEVERE
condensation on the jointer. It was literally puddling up on the tables. I
was mystified. I checked the tablesaw surfaces - no condensation. I
checked the bandsaw table - nothing. I even looked at a few of my
handplanes, etc. and no sign of condensation - it was just happening on the
jointer.
Does this make any sense?? It sure explains why the jointer is suffering
the most from rust, but I don't really get why the jointer surfaces would be
so much colder than the rest of the tools, which is the only reason
condensation would preferentially occur there. Has anyone else experienced
this kind of thing?
I've been trying to beat the rust problem for years and finally feel
like I have it under control. Here's a few of the things I think I've
learned.
Atmospheric Moisture is a byproduct of combustion. The RH of the shop
air may not change that much as you run the heater, because the
increasingly warm air can handle the increasing amount of moisture
generated by the combustion process, but the absolute moisture content
is driven way up.
The RH of the shop air is not the problem. It is the RH of the
microclimate right next to the cast iron surfaces that is the problem.
The cast iron, having a great deal of thermal mass, cannot react to
temperature changes fast enough and stays cold enough so that, with
the temperature/humidity level rising quickly in the shop's air - the
cast winds up being below the dew point - and rust begins to form.
The jointer, having greater thermal mass than the other machinery, due
to the thickness of the castings, shows the rust first.
The solution that I finally came to was to put my kero fired
salamander on a timed thermostat. The thermostat is a plug in style
from Grainger and the timer is one of those cheap things that you can
use to turn lights on and off with.
I set the timer to turn the heater on to about fifty degrees for an
hour or so before I go out to the shop. This allows the shop to warm
up more gradually and thus avoid the air becoming too warm/moist too
quickly. I had to fool around with where to put the thermostat in
relation to where the hot air shot out of the salamander. If you put
it entirely out of the warm air stream it will call for heat for too
long and the air will heat too quickly. It's better to have the
thermostat close enough to the air stream that the heater cycles on
and off more than you would want for normal operation. When you come
into the shop in the morning you can move the thermostat to a more
normal position.
The other thing that I found out about rust is that wax doesn't work
in my shop and neither does TopCote. Boeshield will work if applied
heavy and left to dry without wiping but the result is too waxy for a
daily use tool.
A few months ago I decided to try dewaxed shellac. It works better
than anything I've ever tried. It goes on fast. There's no concern
about introducing bad stuff onto the wood surface. It's cheap. It's
easy to reapply. It provides a slick surface. . .(and it makes the
tools look great).
Good luck.
(tom - rustless at last)
Thomas J. Watson-Cabinetmaker (ret)
Real Email is: tjwatson1ATcomcastDOTnet
Website:
http://home.comcast.net/~tjwatson1