Question about rust

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Hi again,
Well, I just posted about my pleasant table saw tuning experience, so I have to offset that with a bit of a frustration.
Before I tuned the saw, I cleaned the surface of some light rust. I live in CT and this winter has been VERY cold. My shop is in a dedicated bay of a two-car garage, but there's a stud wall separating the two bays (a door gives access between them). The "shop" is about 6 feet wider and deeper than a "typical" garage bay, which puts it at about 16'x24'. The walls are all insulated, but there are two fairly large windows, two sky lights, and the garage door isn't insulated.
I heat the shop with an 80,000 BTU propane heater, which generally does a pretty good job. A few weeks ago when the outside temperature was about 35-40 deg. F, I was able to get the shop from about 40 degrees to about 75 degrees in maybe 20-30 minutes. Today, the shop was at a nice and cool 21.5 degrees F and it took a LOT longer (about 1.5 hours) to get to 70 degrees.
Now to the rust question, the light rust that I found on my table saw wasn't too big a deal. I just sprayed the surface liberally with WD-40 and let it sit for maybe 10 minutes, then used a green scotch brite pad and my ROS to buff it off. Then I sprayed it with some Topcote and a good layer of paste wax.
Last week I had to do the same thing to my jointer (the 6" Delta professional). The only thing different was the amount and severity of the rust. The jointer had some pretty thick rust and it was on just about every cast iron surface on the tool. It took me a LOT of effort to remove it, even though the table saw and jointer had sat idle about the same amount of time.
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 read the interesting review of rust removal and preventative agents in the latest Wood magazine and I have some Boeshield on order. I hope it does the trick, because I don't want to have to deal with this every week or two when I need to use the jointer.
Sorry for the long-winded post, but hopefully someone has some insight into this.
Mike
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Is the jointer closer to the uninsulated garage door?

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nope, the table saw sits right in front of it (about 4 feet away). The jointer is next to the table saw, and is probably the same distance from the regular access door, but I would think that door provides more insulation. Honestly, the garage is cold as hell and I doubt there's much variation within the space. Even when I turn on the heater, you can detect clear zones for some time until the heat has time to thoroughly do its job. The bandsaw is actually right up against an outside wall, and I haven't seen a lick of rust on that table the whole time I've owned it (and I only but a coat of Topcote on it when I first tuned it up).
Mike
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The only reason that I can think of why your jointer would be worse than the other tools would be because the cast iron in the jointer is thicker than the other tools and doesn't heat up at the same rate.
todd
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the
That's what I was thinking. The underside of the jointer table may not get as much airflow either. The warmth from the heater may be driving moisture into the air from all over the shop, and the jointer stays cold enough to start collecting it. A dehumidifier might be a good idea - start it up as soon as the heater is turned on, and park it next to the jointer. -Wm
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Mike in Mystic wrote:

I think it has more to do with the mass of the castings rather than just the temperature. The jointer is probably taking longer to heat up. two weeks ago I turned on the hat and went back to the house to let it warm up. When I returned, the tablesawy had a coating of ice on top from the condensation. At that point, I cleaned it up, turned off the heat, and read a book instead of woodworking. Going from a minus zero to working comfort just is not happening. I'm not trying tomorrow either. -4 expected tonight.
--
Ed
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When you burn hydrocarbons like propane, what do you get (ideally)? CO2 + H2O. Unless you are using a vented heater, you are adding humidity. This is condensed by a cold object in warm air. Advice (free) 1. Use a vented heater or electric or steam heat. 2. Try to prevent those large chunks of iron from getting so cold. Some have tried a light bulb near the saw. I would prefer a small electric heater blowing on it. An old electric blanket would probably work, but might not be safe unattended.
Mike in Mystic wrote:

--

Gerald Ross
Cochran, GA
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Gerald Ross wrote:

Good advice but not very practical for most of us. The cost of heating a detached garage for the 6 days and 18 hours that I don't use it in a week would buy me some nice wood to work on in milder weather. When the temperature gets to -12 like it did a couple of weeks ago, that light bulb is not going to help much. .
Electric heat means adding new service to the garage, maybe to the house for the extra load. Steam heat means keeping the temperature above freezing all the time and is expensive to install.
--
Ed
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I agree with , Ed, although thanks for the suggestions Gerald.
I just can't afford to install much more for heat than what I'm using - a simple job site (non-vented, as you surmised) propane heater. I understand about the source of the condensation, I just didn't expect there to be such a difference in how the different cast iron surfaces in the shop behaved in that environment.
I haven't seen ice yet, Ed, and my goal is to get about 5 or 6 hours of shop time in today, but maybe I'm being too optimistic. I never thought I'd say this, but I'd rather have 2 feet of snow than this cold f&&king temperature. I don't physically mind it, but interfering with shop time makes me grrrrrrrrrrrrrrrrrrrrrrrrrr.
Mike

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I would try that as well. Maybe run it full time. Tony D.
A dehumidifier might be a good idea - start it up as soon as the heater is turned on, and park it next to the jointer. -Wm
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A dehumidifier will also help to heat the garage, just as much as any electric resistance heater with the same power consumption. (Probably not much compared to that propane heater.)
--

FF

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I read somewhere that when propanes burns it increases the amopunt of water vapor by 4X (four times). That seems to be true because the amount of humidity jumps when I run propane in my shop.
On 25 Jan 2004 13:11:32 -0800, snipped-for-privacy@spamcop.net (Fred the Red Shirt) wrote:

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It's all in how you measure things --
One cu.ft. of propane, when burned, creates approximately 4 cu.ft. of water vapor.
One lb of propane, when burned, creates approximately 2-1/4 lbs of water (in vapor form, of course.) This is roughly 35 fl.oz.

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Robert Bonomi wrote:

How does this happen? You mean that propane (or any other fuel) can create more mass that what is was before being burned? If this is true, why don't we ship propane to drought stricken regions and burn it to make water?
--
Ed
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Hi Ed,
The oxygen in the water isn't coming from the propane, it's coming from the air. 2 of the mass units in water are from propane, but 16 (the oxygen) are from air. If you work it out stochiometrically it makes sense.
I'm starting to wonder if it would be cheaper to get a highly insulated garage door, and maybe put R-30 in the walls and get rid of the windows in the garage. I've had to de-rust my jointer the last 3 times i used it. Today I could almost literally watch the rust form on it. From the time I went it until I left (about 3 hours) the rust probably doubled in quantity - from a light coating, to a pretty moderate to large amount.
I think i'm going to try Tom's dewaxed shellac idea. It's the cheapest and most direct. I don't have any idea how I'd rig up the thermostat/timer thing. The problem being, I usually only get out there on weekends, and lately only 3-4 hours at a time.
Oh well, I guess this is life.
Mike

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Mike in Mystic wrote:

OK, but Robert says it "creates" water in vapor form. If it is in the air, it is vapor and does not have to be created. Raising the temperature changes the relative humidity and the dew point and thus the condensation. If there is water in the propane it can be released to the air in the form of vapor. Or a chemcial reaction can change one physical item to another, such as milk into cheese. I just don't know of any mass that can be changed to another form and make a greater mass though.
--
Ed
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Robert knows _generally_ knows what he's talking about.
I'm sure of that -- he's me. <grin>
In this case, I _do_ have the theory right, but was giving propane credit for being about 30% lighter than it actually is -- correct figures below.
This is "Basic Chemistry". What's going on is the 'chemical reaction' you alluded to.
"Created" _is_ the correct term.
Propane *doesn't* burn "all by itself".
One has to have oxygen present as well. Whether there is _any_ water vapor present in the 'air' is _irrelevant_. OXYGEN, on the other hand, is critical.
The chemical reaction:
(1) C3H8 + (5) O2 => (3) CO2 + (4) H2O(gas) + (1996.04 BTU/mole) or "one molecule of propane, together with five molecules of oxygen produces three molecules of carbon-dioxide and four molecules of water and liberates '1996.04/(6.022*10^23) BTU' heat in the process" { Note: 1.552 oz (44 grams) by weight, of propane when burned completely, gives off approx 1996.04 BTUs of heat -- an additional 4752 BTUs can be liberated if all the created water vapor is reduced to liquid.)
Due to the differing atomic weights, things work out (by *mass*) as:
1-3/8 lb propane + 5 lb oxygen => 4-1/8 lb CO2 + 2-1/4 lb water
As should be obvious,this is "6-3/8 lbs in" and "6-3/8 lbs out".
Mass *is* preserved; you just have to account for _everything_ in the reaction.
Of the 2-1/4 lbs of water 'created', only 1/4 lb of that total weight comes from components of the propane. The other 2 lbs comes from the oxygen in the air. The remaining 1-1/8 lb of the weight of the propane, in conjunction with 3 lbs of oxygen in the air, turns into 4-1/8 lbs of carbon-dioxide.
Regardless of however much water vapor _was_ in the air before you lit the fire, after burning 1-3/8 pounds of propane, there is an *additional* 2-1/4 lbs of water "somewhere", either in the air as water vapor, or having 'condensed out' on something. (like the tables of a cold jointer :)
A final note: "This material _will_ be on the exam on Friday!"
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snipped-for-privacy@host122.r-bonomi.com (Robert Bonomi) wrote in

Thank you! Excellent explanation. It should end all debate on the matter. But since when have the facts stoped someone from arguing?
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Ok, this makes much sense. It was not the facts, but the limited explanation in question. It sounded like mass was being created, but it is only changing form. Ed (but I'm still not looking forward to the exam on Friday)
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Yes, it does. Water vapor is one of the combustion byproducts of burning propane -- and of burning nearly anything else that contains hydrogen.

The fact that there is water vapor already present in the air is not relevant. Burning propane adds more water vapor to what is already there.

Adding more water vapor to the air also changes the relative humidity, but in the opposite direction.

No, the water is not in the propane. It is created by chemical reaction when the propane is burnt.

The propane is not merely being changed into another form. The carbon and hydrogen in the propane are being chemically combined with oxygen to form carbon dioxide, water vapor, and probably small amounts of carbon monoxide as well. The mass of these compounds is precisely equal to the *combined* masses of the propane *and* the oxygen it combines with -- which clearly is *greater* than the mass of the propane alone.
-- Doug Miller (alphageek at milmac dot com)
How come we choose from just two people to run for president and 50 for Miss America?
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