For all the masons and rockhounds out there.
Looking at incorporating a big oldtime New England style fireplace into our remodel. I would like to use the same stone for the firebox as for the outside in a classic old time look and feel.
Question?: Wouldn’t most stone crack under the repeated heating and cooling and if not what type of stone would be a good choice?
Replies
I think most stone wouldn't crack as long as its dense.
Make a firepit outside with the stones you like and make several roaring campfires in them to check it out.
Be bringin marshmellows and Chardoney
andy
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The method used by primitive people for splitting stones was to heat them in a fire.
Today, using a torch on granitie is a way to create a split edge finish on cutt stone blocks.
Any river rock ( smooth and round) that has been in water or underground has moisture in it. That moisture can possibly create steam in a fire and send fragments flying.
I would use firebrick for your firebox. there are old slum ones available.
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thee: ...there are old slum ones available.
me: ?..."there's enough for everyone"
typo
not 'slump' either. LOL
I meant to say 'slim'
Also - most fireboxes get built with the face of the firebrick large side out to view, but my mason - on these old places - will lay them with the slim side facing you on the flat like normal bricks and will use refractory cement for a really tight mortar joint. Looks sharp! Uses more fire brick and costs more though.
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what is the nature of 'refractory' cement? - - they just look at me strange when I ask for it around here...years ago I got some in a can when I was working on a woodstove... I assume something must be availible in a bag for jobs such as you describe..."there's enough for everyone"
David,
Rutland makes a refractory mortar. AP Greene carries some stuff too. If your local brick yard doesn't have something ask at a pottery supply store. Potters use it to build big kilns. Refactory cement is usually used as a castable to make walls in kilns. When these refactories cure they give up all their water and have lots of small air bubbles so they resist heat better.
KK
we always lay them slim side showing because it gives the neccessary mass to the firebox... so it not only looks better it is better...
my first fireplace i laid up the box with refractory cement mortar..
the only thing about refractory ( and why it doesn't get used as much ) is the at it takes a long time to set.. and the bricks keep squeezing the mortar out.. it is VERY plastic..
normally with common mortar, you can just keep laying .. the mortar takes enough set to support the next course..
with refractory. you often have to lay one course and come back the next day for the 2d one..
refractory is a superior mortar for a firebox though.... but i never see it used anymoreMike Smith Rhode Island : Design / Build / Repair / Restore
Don't know about the chemical makeup, but you can get it in one gallon, two gallon, and five gallon sizes, as far as I know, premixed.
It handles temps up to about 3000°F and some kinds will also handle acids better too. ( Important because you get more sulfuric acid in even oil burners nowdays) The creosote also has some acids.
A normal mortar joint is 3/8" but the refractory seems to handle 1/4" or slightly less better - probably with a finer aggregate.
The temp rating is important where uyou will have hot fireplace fires - or in chimnneys wheere a chimney fiore is likely. Temps in a chimney fire can exceed 2200°F with no trouble. That will damage normal mortar so we have the clay flue tiles set with refractory also.
BTW, I t is much harder on bare skin. Wear rubber gloves with it.
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Try asking for "fire clay". I haven't bought any for years ( I used to rebuild fireplaces when I was a younger man ). They used to sell it at the brickyards - you mixed it with type M mortar and unfortunately I don't remember the suggested ratio. It may have been some kind of asbestos sh!t.
I invented asbestos.
"fire clay" is only a clay....no asbestos.
It is used in building ceramic kilns, brick ovens, rotary kilns and the like, as well as fieplace fireboxes, where the fire brick are layed by dipping them in a batter made from straight fireclay.
This leaves a very thin mortar line ( 1/8"-1/4") and when fired, hardens into heat resistant joint.
By using the dip method there is no "wait to dry" time or "oozing" of bedding joints as you will find with refractory cements.
.....................Iron Helix
PS....I would "vote" for the firebrick rather than natural stone. Most sedimentary and metamorphic stone will break down with repeated high heat cycles.....meaning a firebox rebuild sooner than you think!
Edited 11/16/2004 7:12 am ET by Iron Helix
"Today, using a torch on granitie is a way to create a split edge finish on cutt stone blocks."
I just learned that trick from my stone vendor a couple of days ago while I was picking out a chunk of marble for a pastry slab. Watering the edge down first gives a little better results. It's kind of fun in a blowing-up-little-green-army-men kind of way too.
I see a lot of Soapstone used on masonry stoves and heaters. I'm guessing it doesn't split because of its mass, and because it doesn't absorb moisture like other stones. Do you know if Soapstone can be mortared in or does a stone need to be able to pull a little moisture out of the mortar to lock it all together?
I don't know. it could be that the right adhesive would be a suction type like silicones - not that I'd recommend that one.
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I agree with Andy. Build a stone wall outside. Make a hot, hot fire right up against it and see what pops.
If you do use stone, make a couple of small fires in the fireplace and get the stones good and dry before you build a really hot fire.
Granite flakes under a high thermal gradient. Put something real hot against the outside, like a propane or MAPP flame, while the inside is cool, and a chip will pop off. I don't think splitting or exploding is a serious risk for dry granite in the back wall of a fireplace.
IIRC, the stone they use in Hawaii for a luau is basalt, because it can be put right in the fire without risk of bursting.
The old time NE fireplaces I lived with when I was living in VT (all dating from the mid 1800's) where all built with firebrick in the firebox.
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