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gjbingham 10-25-2007 07:55 AM

Mortar set time in cold weather
Hi all,

Anybody know how wet cold weather affects the set time of mortar? I'm planning on using the fireclay/lime/sand mix instead of Refmix. It was 36 degrees this morning. I'm not expecting warm weather anytime soon.

Also, I'm planning on using a canopy and tarp to cover my work this fall, but I'm curious what effect rain would have on the mortar and floor of the oven if it got rained on during the occasional extreme weather here in WA State. I can envision the fireclay/sand mix used in setting the floor washing out, resulting in an uneven floor.

Thanks for your thoughts.

sarah h 10-25-2007 09:26 AM

Re: Mortar set time in cold weather
I know that using cold water to mix Heat Stop will keep it more workable a bit longer and it seems that working in cooler, humid weather does too ... but I'm not sure if that applies to all mortars.
I've been working under a canopy but also using a tarp in bad weather. I monitor carefully, when it's tarped, for condensation. I find that, being under the canopy as well, it's easy to flip the tarp to the 'dry' side or adjust air flow even if it's pouring rain.


Unofornaio 10-25-2007 11:48 PM

Re: Mortar set time in cold weather
Wait a min fire clay, lime and cement? If cement is just implied then the mix you are using (fire clay, lime, sand, cement) really doesn't "set" like regular mortar, it more like dries out. The rain will damage that mix when still soft but not after it has hardened and will wash away the fire clay/sand mix from the hearth. Not so much the cold but moisture will extend its drying time. It will be cured (gain its full strength) only after its been fired.

gjbingham 10-26-2007 07:03 PM

Re: Mortar set time in cold weather
Implied cement included in the mix is correct. Sorry, I was being lazy.

It sounds like you do agree that the sand/clay mix under the floor would indeed wash out if rained on. I did set the oven floor today and used only fireclay. It will probably freeze tonight. I'm waiting to see if the bricks heave.

Thanks for both your help!

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