The big thaw and rust

[Bluekingfisher]

Despite having an insulated and dry workshop and keeping my cast iron tools waxed and well oiled I noticed while pottering around last Saturday most of my cast iron tools were 'sweating' from I can only assume the abrupt temperature change. I was initially a little concerned but as I have had my present set up for 5 - 6 years I have never suffered from condensation or rust so assumed the issue would only be temporary and normal.

However, I had cause to visit the workshop last night and found to my horror a great deal of my tools have turned poop brown. I had a go at removing it from the worst affected tools however it took a little more than gentle elbow grease to remove the rust from the one of two tools I attempted to clean up.

I only mention this as this has never happened to me previously and perhaps those of you with cast iron tools may wish to check on them sooner rather than later, particularly if you haven't seen them for a while or your shop is not well insulated.

Good luck

David

 

[DennisCA]

Don't you heat your shop? If you don't, that's the cause.

 

[Jacob]

Yep. Humid air hitting cold surfaces. Solved by heating, and also by closing ventilation off if the workshop is left for long; keeps warm air in and humid air out.

 

[Spindle]

Hi

Sorry to hear that, hope you caught it in time.

The rapid thaw after the cold spell was indeed responsible - your larger tools had 'cold soaked' and lagged significantly behind the surrounding air during the warming up. Result, damp air in contact with a cooler surface and condensation is formed.

As Denis said, the solution is to heat - the tools, if not the workshop.

Regards Mick

 

[ED65]

Sorry to hear that David, having recently seen your wonderful tool storage in that other thread you've got a lot of work ahead of you! Best of luck with it mate.

 

[Bluekingfisher]

Thanks for the feedback boys.

Ironically, I did heat the shop on the Saturday (after the air had become a little warmer than preceding days) with an electric fan heater. Perhaps I should have left it on for longer to dry the air a tad more.

The most badly affected tools were the ones closer to the heat source?

David

 

[Spindle]

Hi

A heater will only warm a space it will not dry it - in order to do that you need to remove the moisture by either absorbtion, (desiccant), or removal, (ventilation).

Ironically heating the air increases its capacity to retain moisture.

Regards Mick

 

[shed9]

Sorry to hear that David, having recently seen your wonderful tool storage in that other thread you've got a lot of work ahead of you! Best of luck with it mate.

Ditto, hope you caught this in time and that it is just surface problems.

 

[Jacob]

Hi

A heater will only warm a space it will not dry it - in order to do that you need to remove the moisture by either absorbtion, (desiccant), or removal, (ventilation).

Ironically heating the air increases its capacity to retain moisture.

Regards Mick

Wrong. Heater will dry. It's the old relative/absolute humidity issue. Right in that it won't alter the absolute humidity of the air - it will actually increase it by taking moisture from surfaces (if it's there) but it will reduce the relative humidity and warm surfaces beyond the dew point.

 

[Spindle]

Hi Jacob

I think you'll find I'm correct, in that the space will not be dried.

Warming the air will as you say increase its capacity to hold moisture and condensate will be reduced / removed, however it will condense out again once a cooler surface, (below the dew point), becomes available.

In my head drying involves the removal of moisture :wink: .

Regards Mick

 

[DennisCA]

Hi

A heater will only warm a space it will not dry it - in order to do that you need to remove the moisture by either absorbtion, (desiccant), or removal, (ventilation).

Ironically heating the air increases its capacity to retain moisture.

Regards Mick

That's how it dries out the air in your shop. Warm air holds more moisture, yes so when you warm up the air in your shop it absorbs moisture from your interior space, then this moisture laden air is ventilated it out and new colder outside air is brought in and that holds less moisture. Now you repeat the cycle and the moisture content in your indoor space will keep going down until a certain point. This is how an interior space (basically all houses) is dehumidified via heating.

 

[Spindle]

So we agree then

 

[DennisCA]

Upon closer inspection it appears we do

 

[Jacob]

Hmm.
Warmth does dry "space" even if air isn't exchanged. Even in a sealed room heated air will take up moisture from damp surfaces/materials and in warming them will keep them above dew point. This will go into reverse if the heating is withdrawn of course - but the coldest surfaces get the condensation first, most likely the windows.
Ventilation alone will not dry the space - which is what the OP observed. Warm (and hence more humid) air enters a cold building and condenses on cold surfaces.
You really notice this in unheated but ventilated buildings when a big enough change in the weather brings warmer and more humid air into contact with the cool building/contents and causes condensation everywhere. Or sometimes just locally where things near a window get cooled below dew point - condensation on the window and on the plane you left on the window cill!

 

[AJB Temple]

Ultra confusing. I feel I need an idiots guide to ho two stop condensation in my unheated workshop.

 

[Spindle]

Hi

That's easy - insulate the workshop to slow down the rate of temperature change - this allows the larger machines time to keep closer pace with the rate of temperature change in the atmosphere.

Ventilate when the workshop is in use and it's dry outside.

If your workshop is subject to moisture, (leaks, damp, brought in on materials), you should maintain ventilation at all times.

Regards Mick

 

[Jacob]

Ultra confusing. I feel I need an idiots guide to ho two stop condensation in my unheated workshop.

Keep it simple - you need as much heat as you can afford (or feel comfortable with) and/or as little ventilation as you need to breathe.

 

[Bedrock]

I bought an oil-filled radiator which provides background heating, at what seems to be a relatively cost, plus I insulated my workshop. Rust is now a very rare occurrence.

 

[D_W]

If you can keep the shop below about 63% humidity, you shouldn't have rust. Easier said than done, maybe. I'd try for making it more airtight and insulated so that it doesn't change temperature quickly. If the amount of moisture in the air in the shop is constant, but the temperature drops quickly, you'll still go above the relative humidity threshold.

 

[David C]

I would hope that 0000 wire wool and Autosol, or some other chrome cleaner would shift the surface rust.

Then oil surfaces.

David Charlesworth