Old 07-30-2010, 06:43 PM
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Join Date: Jul 2005
Location: New Jersey USA
Posts: 4,216
Default Re: Oven Dome Mortar Mix?

The term "silica sand" is misleading because that's what sand is: silica, or quartz busted up into little pieces.
My geodesic oven project:
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Old 07-31-2010, 06:40 AM
Join Date: Jun 2008
Location: ohio
Posts: 21
Default Re: Oven Dome Mortar Mix?

Sand can have a lot of different minerals in it and still be called sand but silica sand is considered more pure and is not as likely to explode under high heat. Little pieces of sandstone can still hold water and when heated can expand and blow apart. Silica sand is from quartz rock and is very stable under high heat, very pure silica sand is used in making glass.
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Old 11-13-2010, 07:27 PM
Join Date: Oct 2005
Location: Gilbert, AZ
Posts: 423
Default Re: Oven Dome Mortar Mix?


Get the 30 Grit silica sand. Sometimes, my local HD/Lowes will have it in super sacks of about 500 lb for the price of 2.5 sacs of regular! It has been great mixing my own mud with the stuff for the last few days!
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Old 11-14-2010, 11:06 AM
Join Date: Aug 2010
Location: Glendale, Arizona
Posts: 397
Default Re: Oven Dome Mortar Mix?

Hi EricU,

Did anyone answer your specific question about the correct mortar mix? There are several variations and ratios mentioned on the forum when I searched. I recently used 1: 1: 1: 9, fire clay, Portland, hydrated lime, 60 mesh sand, for a small job. I thought the mix was a little heavy on the sand but it handled well and hardened up just fine. Other mixes use more Portland, fire clay and lime. Here is a mix recommended by a popular oven builder who has his own site. 10 sand: 6 clay: 2 Portland: 3 lime.

As to the sand issue, I found silica sand easily at HD, builders supply and brick yards. It is often used for sand blasting and it comes in various mesh sizes (as previously mentioned). I've used both 60 and 120 mesh without any noticeable difference. Fire clay is easy to find at the builders supply stores. My local HD stores didn't carry it.

I used HeatStop 50 for the joints in my precast oven panels and some chimney joints. It is rock solid when the joints are thin. There is shrinkage cracking on joints over 1/4", but that is to be expected since joints of that size and larger are not recommended. The "cracks" appear between the bricks and not along an edge. I just smeared in a bit of fresh mix with my finger the next day and there was no more apparent "cracking". I like HS 50 since a little goes a long way if you use thin joints. You can fill the larger gaps with home made refractory mortar. See "Combine Mortars" in the Newbie Forum.

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Old 11-16-2010, 01:12 AM
Join Date: Dec 2009
Location: Christchurch, New Zealand
Posts: 78
Default Re: Oven Dome Mortar Mix?

Hello I'm about to start laying bricks. couple of questions?
1/ Is there a recommend method to mixing?
2/ I hear lime can burn as its costic is this true?
3/ Any other last minute advice?


http://www.fornobravo.com/forum/f2/o...-nz-14012.html (Oven Build 900mm - NZ)
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Old 11-16-2010, 04:50 AM
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Il Pizzaiolo
Join Date: Oct 2009
Location: Ausitn
Posts: 3,292
Default Re: Oven Dome Mortar Mix?

Portland and lime are both very caustic when wet. Wear gloves or barrier cream at least, and try to keep your hands dry. Mix small amounts until you get a feel for the pot life of your mix.
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Old 11-16-2010, 08:07 AM
Join Date: Aug 2010
Location: Glendale, Arizona
Posts: 397
Default Re: Oven Dome Mortar Mix?

Hi Wemme,

Yep, Portland cement and lime will dry out the skin on your hands quickly. Then you've got this sandy feeling on them for a couple of days. Home Depot sells a 5-pack of vinyl coated cloth gloves that are great when mixing and working with mortar/cement. I often put on nitrile gloves first then with the HD gloves. If you need to handle raw mortar with your hands then you are protected. The gloves are light weight, clean up easily and dry overnight for reuse the next day. Also, don't breathe the dust from cement or lime...... Cough, cough !!

Best of luck for your project,
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Old 11-16-2010, 01:07 PM
Join Date: Aug 2009
Location: grand rapids, michigan
Posts: 139
Default Re: Oven Dome Mortar Mix?

hi Eric, i used refractory mortar, it was called Derby 3000, came in a black pail with a red top. 3 gallon pail, just a little thicker than drywall mud. the beauty of the stuff is that i could get home from work, open the pail and work for 15 minutes if i wanted to and all i had to do to clean up was throw my trowel in a pail of water and put the lid back on the bucket. I used 2 pails in my 36" build. i didn't fill the brick voids with the stuff though, i only used enough to set the bricks together... then i used home brew in a grout bag and filled the backs, using a hard plastic float to work the mortar in. i parged about 3/4" thick with home brew...
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