How much water is in the water vapor? I'm not doubing the statistics, but you are saying that 10 cu. ft of air reduces to 16% of vapor by volume. What else is included here in the 1.6 cubic feet? That means that the original atmosphere contain 16 percent vapor, but that must be reduced to a given amount of liquid. How do we calculate the liquid content?
I guess I must be extremely lucky - I'm doing something right. I've got a small shop in an unheated outbuilding and I live where the humidity is low in summer and high in winter. So the tools sit unused for a lot of the winter in a cold and damp shop.
The only time I've seen rust on either the jointer or the tablesaw was right after I bought them. And, to be truthful, the time I set a bunch of green wood on the tablesaw for 24 hours or more :-).
When I first saw the rust shortly after purchase, I started waxing the tops with Johnsons Floor Wax. I do it two or three times a year. It works, and I suspect any similar wax would also work.
If you use your cast iron tools every day, you might have to wax more often. I'm not sure about that, as I suspect the wax gets down into the pores of the cast iron and resists rubbing off. So that's just a guess.
You may want to warm up the shop SLOWER next time, the cast iron is heating up slower than the air and the temp difference is causign the condensation.
As to why it is being seen the most on the jointer is a puzzle
John
Mike,
Tom Watson had an interesting post on this not too long ago, wherein he reported on using shellac as a coating that was more effective than all the standard ones at preventing rust. Have a look at it at:
Regards, H.
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.)
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:
The reason you get the 'preferential condensation' is that the jointer isn't warming up _as_fast_ as the other stuff.
This can occur for several reasons:
1) mass of the metal, relative to exposed areas. The more mass, per unit of 'exposed area', the _slower_ it warms up. The larger the temperature differential, the more condensation. (all else being equal) 2) _location_ in the space, a) poor air circulation around it, means slower warming. b) absent something to 'keep the air stirred up', temperatures are not likely to be uniform throughout the space. 3) The heater is a non-trivial source of humidity. *anything* that burns hydrocarbons is such a source. The reason: C(many)H(some) + {many+some/4}O(2) => {many}CO(2) + {some/2}H(2)OPropane is "C(3)H(8)", thus you get 4 cu. ft. of water vapor for every cu. ft. of propane you burn. Or about 35 fl. oz of water, per pound of propane.
4) Humidity _will_ migrate into colder air, faster than heat does. The 'why' is involved. but the result is that the colder spots tend to have higher relative humidity, which contributes to the condensation.
The active component in Coca Cola, or any other "cola" flavor for that matter, is _phosphoric_acid_. The operative word is "acid" -- it =will= 'eat things'.
Navel jelly is *bad*news*(tm) for tools/tooling.
For iron parts, electrolysis is the best method. it _restores_ the iron surface.
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.
The answer to your last question is "absolute humidity". the math gets somewhat messy. Google for a write-up. :)
Air consists partly of oxygen. the oxygen is the only part that is involved in combustion.
The amount of oxygen in 10 cu. ft. of air will combine with a 'fuel' to "make" about 1.6 cu. ft. of water vapor.
If you want to go through the actual numbers -- You start with the percentage of 'air' that is oxygen. the oxygen molecule ("O2") has a molecular weight of 32 (roughly). thus 22.4 liters of O2 will weight 32 grams.
Propane (C3H8, molecular weight 32) provides the hydrogen.
1 C3H8 + 5 O2 => 3 CO2 + 4 H20 + {heat}CO2 weighs in at 40, and H20 at 18
In gaseous form (at standard temperature and pressure), 22.4 liters of -anything- weighs, in grams, what the molecular weight of an individual molecule is.
Have fun with the math.
One lb of propane, when burned, generates about 2-1/4 lbs of water. or about
35 fl. oz.A dehumidifier will add MORE heat than a electric resistance heater with the same power consumption.
It's obvious that all watts consumed by the dehumidifier will stay in the garage as heat. What is not so obvious is that when water vapor condenses into a liquid it gives up heat (just the opposite of what happens when it evaporates). There is also the heat pump effect of removing heat energy from the cold condensate if it is piped down a drain.
Art
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?
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
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.
to burn 1 pound of propane, takes _5_ pounds of Oxygen in the air.
From which, you get approximately 2-1/4 pounds of water, and 2-3/4 pounds of carbon-dioxide.
Robert knows _generally_ knows what he's talking about.
I'm sure of that -- he's me.
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){heat} 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 waterAs 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!"
That's actually 1-3/8 pounds of propane. not one pound. I was using the wrong weight for propane.
Correction: 3-1/8 lbs of carbon-dioxide.
Yawp. *lots* of heat.
Approximately 970 BTUs _per_pound_ of water condensed. That's enough heat to raise the temperature of 10 lbs of water by nearly 100 F.
Or, 8,200 BTUs per gallon of condensate.
For the metric crowd, 540 calories per gram. Enough to raise 10 grams of water by 54 C.
The effect of this is _trivial_ in comparison to the condensation.
If the water is at 20F below 'room temperature', that's a whopping TWENTY BTUs per pound of water that goes down the drain. About 1/5 of 1% of the energy released by condensation. Hardly worth mentioning. :)
OOPS! propane is actually molecular weight 44
With the above-mentioned correction, that's 1-3/8 lbs of propane.
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