Thank you for bringing up this VERY important question & thanks to @bikerbudmatt for flagging this message.
I really need to sit down w/ a hot cup of Woods Coffee and spend a couple of hours on this one question. But right now I’m tapped for time, so I’m going to give you a list of Pro’s / Con’s of pre-mixed High Temp Mortar, until I get a chance to spend the proper amount of time that this question deserves.
The following is my experience w/ Sairset by Harbison Walker International
PROS:
- Fairly Priced - Bucket or Pail
- Excellent Heat Retention characteristics
- Perfectly Blended - No Guesswork
- Great Texture / Workability
CONS:
- Non-Water Soluble (Breaks down / crumbles if it gets wet)
- Can only be used for THIN mortar joints (no more than 1/8").
- Mortar does not harden until it has been fired (mortar touches fire for a specific time period). And the slightest movement can crack those soft mortar joints.
- Can’t support weight! If you place this mortar between two bricks or blocks, the mortar will squeeze out like ketchup under a heavy hamburger bun.
- There are a few more cons… and I’ll add these at a later date. But you have enough now to realize that you DO NOT want to use pre-mixed mortar to build a Mattone Barile or Mattone Barile Grande pizza oven.
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DO NOT USE PRE-MIXED HIGH TEMPERATURE MORTAR ON ANY PRODUCT FROM BRICKWOOD OVENS!
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ONLY USE DRY HIGH-TEMP MORTAR THAT COMES IN A BAG.
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SAVE A TON OF DOUGH BY MAKING YOUR OWN HIGH-TEMP MORTAR WITH A NEAR-PERFECT TRACK RECORD!