Condensation

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We moved into a new place not too long ago, and for the first time I'm getting condensation on my table saw and joiner in the mornings. What's the easy answer? A quilt or blanket over the top?
Thanks,
Michael
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I think if you put either of those you will be in for a big surprise -more rust without question. I make a practice of never leave anything on the cast iron. Anything seems to attract moisture and rust/discolor the top. If you get condensation, maybe plastic would work to stop that. You also should protect the top with something like topcote spray, this is what I use but there are others as well.
Mike Coonrod
Michael wrote:

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Mike Coonrod notes:

No to the plastic if he's getting condensation: it will simply hold more water on its underside.
Best bet: HTC makes some special tool covers that do a superb job. And then add the Topcote, wax, other protector. I once stored a table saw outdoors, using Boeshield T9 (2 coats, neither polished out), and covering it with a top grade canvas/vinyl coated tarp that was flocked on its down side. I put the tarp over 1" styrofoam. Left the saw out all winter and into the spring. Uncovered it and found my only screw-up was in not sealing the tarp seam, which left a bit of a rust line under the styrofoam.
Charlie Self
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What would silica gel do? I see this is now sold in pet stores to add to cat litter.
If you put a tray of silica gel over the table (but not resting directly on it) and under a tarp, do you think it would have much value? I'd still use topcote or something.
Mike
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Silica gel, and other dessicants, are *only* effective in something "close" to a sealed enclosure. It can only absorb a 'limited' amount of moisture, and, once that amount has been absorbed, it is _exactly_ as if the gel wasn't there at all.
There are exactly *three* ways to prevent condensation rusting: 1) no 'bare metal' exposed to the condensation -- coated with wax, TopCote, Boeshield, or 'something else', that prevents any condensate from contacting the metal. 2) keep the *absolute* humidity low enough that condensation doesn't occur. (this is what silica gel does, in a "sealed" environment) 3) keep the temperature _high_ enough that condensation doesn't occur.
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Like most absolute statements, misleading at best. "Ventilation", one of key components of preventing condensation in every scientific study of the subject, is not even mentioned.
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Spoken like a true ignoramus. Ventilation works by 'moving out' the high moisture-content air, and replacing it with (hopefully) lower moisture- content air. This is one 'possible' way to accomplish method #2 -- "reduce the absolute humidity." *ASSUMING* that the replacement air _is_ lower in absolute humidity than the previous air, that is.
"Ventilation" _can_, in some circumstances, make the problem _worse_. i.e., where you are pulling warm moist air into a much cooler space.
Just "moving the air around", e.g., where you 'replace' existent air with other air of the same R.H. and temperature, doesn't do squat for a condensation (and subsequent rusting) problem.
The _physics_ of condensation are "well known". It occurs when the absolute humidity of the atmosphere is higher than the saturation point for water vapor _at_the_temperature_of_the_object_. If that condition is present, condensation occurs; If not, it doesn't. The process *is* just that simple.
You prevent condensation from occurring by keeping the absolute humidity of the air below the saturation point of the "cooler object", or by keeping the temperature of that object above the 'dew point' for the current absolute humidity level.
There simply _aren't_ any other factors to play with.

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My my ... how ad hominen little minds can get when called upon to defend their twaddle.
>Ventilation works by 'moving out' the high

"reduce
<unscientific BS snipped>
Prattling all day about condensation in a mixed up, confused, unscientific and illogical manner doesn't solve the problem, nor shed any light on what to do about it in a wood shop environment where conditions vary from location to location, day to day, season to season.
Nonetheless, anyone so stupid, as you have seemingly done, to discount outright the fact that "Ventilation" may possibly play a BIG part in a simple solution to the problem, deserves exactly what you get ... rust.
Now take your name calling attitude and stick it up your ass.
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OK, dewpoint and dew deposition, are what we're interested in, if you want to be precise.
Don't want your machine below the dewpoint - relative humidity 100% - but, as we know, if it's not far below, air movement will keep the grass dry, as it will with your machine. That's why still air under a cover isn't the best idea given.
I go with dehumidification, because it won't matter much if you've the shiniest tools around if your wood is saturated. It also circulates air, and can be controlled so it's only on when required. Drawback is, it works poorly at low ambient temperatures. More info needed there. Could be warmer's the first part. Consider also that you're going to culture some nice spores in a damp area, and a lot of them are less than healthy for you.
Matter of fact, I dehumidify in my shop in the summer. Now, with dewpoints in the low 30 range, and interior at 70, things are pretty dry.
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I am well informed on the principles of condensation and rust, thanks.
As a practical matter to woodworkers, we have three basic tools that can go a long way toward keeping rust under control in our shops ... a rust preventative on machined surfaces, ventilation, and de-humidifying the air in some manner.
Sometimes one method is enough, more often a combination of two or more is sufficient. Sometimes it takes all three, and then success may not be guaranteed given the wide range of factors and climates we operate in.
As in solving any problem, use of the most efficient and readily available tool at your disposal is the most intelligent course of action to try and solve the problem ... often the solution can be as simple as keeping a fan running in the shop during those times of year that cause the most problem.
Something that simple is certainly worth trying, along with the use of TopCote, etc... as I boringly indicated in another thread.
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Well, not really, given your misuse of terminology.
In practical terms we can avoid the dewpoint by warming the air - effectively dehumidifying by lowering the RH, moving the air, thereby minimizing condensation, or actually dehumidifying, by reducing the absolute humidity.
To say that condensation depends on absolute humidity as you did in an earlier post, without relating it to temperature will only mislead the unknowing and cause snickers among the knowing.
"Ventilation" is misleading as well, since all that is required is motion in the air, not any type of exchange.
Other than that, you're doing OK.

go
problem.
want
but,
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Say what? I stayed far from "terminology" on purpose.

absolute
You got both the wrong string AND the wrong yo yo, Dude ... literally.
Check your sources again, you'll clearly see I never mentioned anything of the sort.
I purposely never mentioned anything more technical than the words "ventilation" and "condensation".

in
Thanks ... but point that gun elsewhere. ;>)
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Say what? I stayed far from "terminology" on purpose.

absolute
You got both the wrong string AND the wrong yo yo, Dude ... literally.
Check your sources again, you'll clearly see I never mentioned anything of the sort.
I purposely never mentioned anything more technical than the words "ventilation" and "condensation".

in
Thanks ... but point that gun elsewhere. ;>)
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George wrote:

"Agitation" then?
I slept through science class when we were talking about meteorological stuff, and I have no clue how any of this stuff about "dewpoint" and "relative humidity" really interacts. I _can_ say that I started leaving my box fan running all the time, and I can pretty much just leave all my metal stuff unwaxed and ignored without any nasty surprises the next morning. Rain or shine, warm or cold, humid or dry, doesn't seem to matter. I've been leaving some stuff sitting out just to see if it will rust, and so far, so good. It's a total shift from the way things were before, where anything unwaxed would be covered in rust after just one night.
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Actually, George is wrong ... "ventilation" in the sense I've used it in this thread is not misleading in the least and contending otherwise is purely a semantics based argument for the sake of same.
Moving air across the surface of your tools is "ventilation" of that surface in _any_ sense of the word.
Your experience with a fan (ventilation) verifies what I've been saying in this thread, as well as my own experience in a couple of different shop climates with keeping a fan running. I live in Houston (read high RH/wild temp swings), and have NO rust problems in my shop... it ain't by accident.
It certainly won't work in every situation, climate, or circumstance, but it is inarguably an economical and cost effective way in those climates/environments where it does work, and certainly worth trying, in combination with other efforts.
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Just keeping air movig will help. Condensation forms due to the warm moist air hitting the cold saw. Keep the saw the same temp, and no more condensation.
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Boeing does seem to put an amount of r&d into their products.
I think your first move would be to determine the mechanism causing the condensation. Where's this moisture coming from and what is allowing the equipment to chill at night and then exposing them to warm air. Is your shop heated by a central heating system and your thermostat programmable?
If you have a moisture problem and wood being a sponge you may eventually have more problems than only rusty tools.
It's amazing how little it takes to keep something from rusting. I set the Craftsman TS on the deck to keep from contaminating the shop with pressure treat while making the decks handrails. I gave the top a good coat of furniture polish/ wax (whatever the Wife had on hand) and covered it with a plastic "drop cloth" that went to the deck and wrapped a rope around it to keep the 'cloth' from blowing off. Then it rained for 20 out of the next 24 days. The top remained surprisingly rust free.
YMMV.
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Try a fan running 24/7 in the vicinity and see if that stops the condensation, plus use of TopCote on machined surfaces.
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Absolutely not -- that will trap moisture against the top and accelerate rust formation.
To prevent condensation, you need to reduce the relative humidity in the shop. This is done by (a) reducing the moisture content of the air in the shop, or (b) raising its temperature.
(a) is best achieved with a dehumidifier, but first try a fan, exhausted outside the shop -- it's cheaper to purchase and to operate. If the fan does the job, no need to spend big bucks on a dehumidifier. If you do need to get a dehumidifier, Whirlpool makes some pretty good ones: quiet, not too expensive, made in the USA.
(b) is achieved in the obvious manner: with a heater.
(b)
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"Michael" wrote ...

Absolutely not! The blanket will trap the moisture against the surface and accelerate the rusting process. I've seen it happen. Your best bet is to protect the surfaces with a coat of good paste wax and try to dehumidify the air. You could buy a dehumidifier but first I would probably try a bucket of that chemical they use on boats. You buy it in marine supply stores. When you get it into the shop you just take the top off and it is supposed to suck up the moisture in the place. You might want to make sure there aren't any cracks or openings where a lot of air is leaking into the shop (or you'll be trying to dehumidify your whole neighborhood) and place the pail somewhere near both the tablesaw and jointer. Eventually, insulation and a vapor barrier will help as well, if you haven't already got them.
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