DOs: Mix it in a clean metal or plastic container. Use only cold clean water. Mix a little bit at a time and install it to familiarize yourself with the product. Use it as a mortar only. Keep the mortar container and your installation out of the sun. If the firebrick or masonry have been stored in the sun or are warm to the touch give them a splash of water prior to installation. This will prevent the brick from sucking water out of the mortar. But don't soak the firebrick as this will lead to efflorescence and weak mortar. Apply heat to the installation anytime after an overnight dry. Be happy!

DON'Ts: Mix the product on a wooden board. Use warm or hot water. Mix the whole bag at one time. Remix or retemper the mortar after twenty minutes approx. Don't expect the product to dry and be as hard to the touch as regular mortar. It is not a structural material. Don't soak the firebrick as this will lead to efflorescence and weak mortar. Don't expect big bonding strength from one firebrick to another. There are no cores in firebrick and they are inherently hard for any mortar to grab onto. Don't use the product as a parge. It is mortar not a stucco. Don't worry!

This list of DOs and DON'Ts grew out of a complaint from a very good mason who thought he did everything right. Here is the complaint .... Your product has great reviews, but not for me. I am using the 50 lb bags of HS50. I have used 4x 50 bags of HeatStop 50 in my outdoor oven. I let it dry for about 2 weeks under cover from rain, then did slow fires to dry out the oven over 5 days. Some of the joints turned white like powder and some joints cracked or perhaps spalled. I could break off any pieces of the joints with my bare fingers. I was afraid that it was the 50 degree weather that I built the oven in April in Concord, MA. I stuccoed over those joints and cracks with a thin coat yesterday, and I can rub the Heat Stop off with my bare hand. My question is do I need to do something else to make it "hard as diamond" as many people say? You do not have any real application do's and don'ts, even under the DIY area, so I am not sure I did a do or a don't? My bags were all in good shape and dry when I bought them, so I am confused as to why the product is performing badly for me? Frank Bob, Can you help out here? Hi Jim: I will call Frank and report back to you later today.. It is rare that we hear anything back from the user and I'll want to follow up on this one. But in the meantime if we were to prepare a list of do's and don'ts for refractory mortar following could be a start for such lists. It also really won't be much different than for any other type of masonry mortar. DOs: Mix it in a clean metal or plastic container. Use only cold clean water. Mix a little bit at a time and install it to familiarize yourself with the product. Use it as a mortar only. Keep the mortar container and your installation out of the sun. If the firebrick or masonry have been stored in the sun or are warm to the touch give them a splash of water prior to installation. This will prevent the brick from sucking water out of the mortar. Apply heat to the installation anytime after an overnight dry. Be happy! DON'Ts: Mix the product on a wooden board. Use warm or hot water. Mix the whole bag at one time. Remix or retemper the mortar after twenty minutes approx. Don't expect the product to dry and be as hard to the touch as regular mortar. It is not a structural material. Don't expect big bonding strength from one firebrick to another. There are no cores in firebrick and they are inherently hard for any mortar to grab onto. Don't use the product as a parge. It is mortar not a stucco. Don't worry! This is only a start to the lists that we can work on later, add to or delete, but may provide some tips to Frank along the way. I will call Frank later this morning but have a couple of comments first. We might find the problem and we might not find the problem but lets try. Heat Stop-50 does not set up hard as a diamond. I did not write that or say it. I suspect the white substance is salt from the flow of moisture containing salts in the brick and the mortar and could be as a result of the project being rained on in the first few days after installation. Beyond that I will call Frank and respond back later. These are only some things to think about. Need to remember to ask Frank what color the bags were. Thanks! Bob Rucker Later .... Hi Jim: I talked to Frank and had a nice chat. He very much appreciated my call back and sharing the e-mail below that I sent to you. I centered my concern on the white stuff coming out of the firebrick and mortar joints and wondered whether he may have left the job uncovered, and perhaps it was rained on prior to getting a good air dry. He said it wasn't left uncovered but did add that he soaked the firebrick for some time prior to installing them. We talked about that a bit and I am thinking that this could be the cause of some of his concern. I have seen it before and never figured it out but perhaps if there is excessive moisture in the firebick prior to installation from either soaking them on purpose or otherwise, it could be the cause of moisture and effloescense leaching back out of the brick and the mortar after installation. This tends to discolor the mortar by making it white and it was these areas only that appeared weak to him. He benefited from the tips provided. In any case he felt that he overstated his case a bit and was a happy camper. He agreed to remove some of the mortar that had the white stuff on it and reinsert some of the same refractory mortar. Nothing further needed. More on the list of do and don't next week..Bob Rucker Back to Refractory Mortar

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