How does an iron cool quickest?

May 11, 2006 8:59 AM

I've finished ironing, and I set aside the iron to cool before putting it away. It's still half-full of water. Will the iron cool down more quickly if I empty the water before it cools down, or after?

I always dump out the water at some point-we've got hard water here, and I don't want scale to build up. But when is optimal?

posted by Chrysostom to Science & Nature (8 answers total)

I would think the sooner the better: the water is adding thermal mass to the iron, storing heat.
posted by slipperywhenwet at 9:06 AM on May 11, 2006

I don't think it will make much difference. The water is used to create steam. It's not really heated until it's dribbled on the the hot iron plate. There is no thermal connection between the water and the iron plate. The water is the resivoir may warm up a few degrees, but that will make no noticable difference in how long it takes the iron to cool to the touch.
posted by cosmicbandito at 9:17 AM on May 11, 2006

If you want to prove cosmic's statement for yourself, let the iron cool to room temp and then turn it on, empty. Use a meat thermometer or the like to determine how long it takes to get up to temp X.

Turn it off, let it cool, try it again with a full reservoir. If there's any notable thermal conductivity it'll take longer to heat up to the same temp.
posted by phearlez at 10:22 AM on May 11, 2006

Don't use tap water in your iron if you want to get the most use out of it. Buy a gallon of distilled water from the grocery store for $1. This will last you at least a year unless you are ironing for a large family.
posted by JJ86 at 10:58 AM on May 11, 2006

Buy a gallon of distilled water from the grocery store for $1.

And given the number of people who get this wrong on batteries and cooling systems: distilled water is not spring water.
posted by mendel at 11:23 AM on May 11, 2006

Most modern consumer-grade irons will tell you in the instruction manual not to use distilled water. Although it may prevent calcium scale, using distilled water will gradually dissolve the innards of your iron. Water normally found on the surface of the earth has some level of natural minerals dissolved in it because that's what water does: it dissolves stuff. When it comes out of your tap, it is usually pretty close to its maximum natural capacity of minerals like iron and calcium, so when the water turns to steam the deposits are left behind. Using distilled water means that the water has plenty of extra capacity to dissolve the metals inside your iron.
Bottom line is that you should probably do what the iron manufacturer tells you to as far as which water to use. If it does clog due to scale, there are a number of ways to deal with it. I recommend one part white vinegar in 5 parts tap water.
To cool your iron the fastest, unplug the iron, dump the water out into a shallow basin, and submerge the hot plate into the water.
posted by leapfrog at 1:31 PM on May 11, 2006

using distilled water will gradually dissolve the innards of your iron

this doesn't make sense to me. the mineral content of tap water comes from the dissolution of ionic solids, not metallic iron. (i don't even know if the metal plate of an iron is actually pure iron; i would presume not, and that it's probably some kind of stainless steel.) i don't think water (distilled or not) will dissolve iron metal. the innards of irons that contact water are probably all plastics anyway.

from a cynical standpoint, the iron manufacturers have something to gain from telling people to use undistilled water, since (i can imagine, anyway) that many uninformed and/or lazy consumers will opt to simply buy a new iron if it clogs with scale deposits.

anyway, i don't buy this.
posted by sergeant sandwich at 4:33 PM on May 11, 2006

Yeah, I could not make sense out of pure water dissolving anything. The inside of irons collect minerals from tap water when the water evaporates. That is where the scale comes from which clogs the iron. Having distilled water without minerals removes that problem. I'm sure with time, distilled water could dissolve anything but I'm guessing that by a few million years, your iron is not going to be working for other reasons.
posted by JJ86 at 8:17 AM on May 12, 2006