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eseemann

coating soft fire brick outside with fire clay slip

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Good Morning Folks,

I was able to pick up a 12 pack of 2600 degree soft fire bricks from Harbison Walker on my way through Salem Va this week and I was thinking about a new 2 or 4 brick forge. I wanted to know if anyone has used fire clay to (for lack of a better term) plaster the outside of the brick so you would have steel box, plaster and then soft fire brick. I was wondering if that might help with the cracking that you get with soft fire brick forges. I think this may not add any value but I have a bag of clay right now so I thought I would ask. I know this will not add to the R value but I wondered about the cracking.

 

thanks

 

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I don't know how your idea would work, but it is worth a try.  I've been repairing my soft firebricks  very successfully with Satanite. I've also put a skim coat of Satanite and crushed brick on the face of the brick that takes the brunt of the burner with good results. 

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The ISFB is not thermally stable... I.e., it will expand/contract as it heats up or cools down.  Therefore, it will crack.  I used a two-bricker forge for four years.  My solution was to coat the exterior with Satanite. Used a torch to heat cure the Satanite.  Still cracked.  I then cut 1" pieces from 1/2" angle aluminum. The pieces were used as edge protectors (to prevent the soft wire from cutting through the SAtanite and into the ISFB). The Satanite gave wear resistance to the ISFB surface, the edge protectors allowed the wire to be tightened to hold everything together.  

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Can you give some specifics for "holding up well" .  We've had folks telling us that their gas forge worked well when it didn't; they just didn't know it.

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2,600f soft fire brick will withstand more heat than the standard 2,300f soft fire brick and it's less susceptible to thermal cycling. 

Coating fire brick with a fire clay kiln wash might help a little but fire brick, hard or soft is made from fire clay. If you use it like an ablative layer so welding flux dissolves the clay  rather than the brick it should work if you replace it often enough. Note how deeply flux erodes the fire clay kiln wash when you use it so you know when to replace it.

A layer of fire clay isn't going to shield deeper layers from the heat, slow it conducting through slightly. To get an idea how much calculate R1 for however thick you coat it. For a decent hands on example think how long it takes the outside of a ceramic coffee mug to get hot when you pour a fresh cup. THAT is how much a layer of fire clay will slow heat loss from the forge. Another relevant factor to add to the calculation being, The more temperature difference the faster it conducts. 170f coffee may take 2 seconds to conduct through the mug but 2,700f cast iron's heat will reach the outside of the mug in milliseconds.

I'm not trying to discourage you guys from thinking about this stuff, I'm just offering you my mistakes so you won't have to make them yourselves.

Frosty The Lucky.

 

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9 hours ago, ThomasPowers said:

Can you give some specifics for "holding up well" .  We've had folks telling us that their gas forge worked well when it didn't; they just didn't know it.

As for "holding up well" 

I've had this forge running about 2 hours at a time until I ran out of propane (20lb) The brick is not cracked, nor showing sign of degradation as of yet. The original poster acquired brick, was wondering about cracking. 

Please explain how other folks didn't know their gas forge wasn't working well and what to look for. That would help me a lot.

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So basically you are saying that your car has great reliability because you have used one tank of gas and nothing broke?

As to how to judge: experience and comparison with other forges.

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Also, we have a constantly expanding choice of products, with an ever greater need to look into their details. There is no is no such thing as just soft and hard bricks anymore; and even the same use rating of bricks, like as 2600, is a poor guide to go by; you need to read and understand their technical references. 

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10 hours ago, ThomasPowers said:

So basically you are saying that your car has great reliability because you have used one tank of gas and nothing broke?

As to how to judge: experience and comparison with other forges.

At some point in time will you share your vast experience and help the original poster with his question? 

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Have you read the posts in this thread? The OP's question has been answered and pretty clearly. If YOU don't understand the answer please ask for clarification but try and be specific enough we can render a meaningful answer. 

If on the other hand you're letting your snark out over Thomas's tendency to show his frustration at impossible to answer questions or meaningless statements perhaps you can take more constructive course and answer them.

Holding up well as compared to WHAT? How many tanks of propane have you emptied through your forge? What kind of fire brick, what rating? You DO know there are several grades of fire brick both hard and soft types. Yes? What temperature does your forge reach?

Without knowing how you measure good or bad, saying it performs well doesn't tell us anything. If you had the experience to have an opinion we knew how to gauge you wouldn't be asking these questions.

Asking poor questions and copping attitude for  not hearing what s/he wanted to hear is how we ended up with the moniker Curmudgeon. 

Frosty The Lucky.

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Not all opinions are equal; I know the internet tries to foster the belief that everyone's opinion has the same worth and EVERYONE should post their opinion whether it is well reasoned or not.  I do not believe this is true. I would prefer that people who do not have the experience not mislead new people who can't tell if it's a good idea or not. (Youtube is a huge source of erroneous information given out as truth!  Look at the threads here on using plaster of paris as a forge liner "just like the guy suggests on youtube")  You yourself must have some beliefs this way or you would not bother to ask blacksmithing questions in a blacksmithing forum; you could ask them in a Baby and Childcare forum or an Dog Breeding forum and accept their answers as being just as good.

Before I trust someone's opinion I like to know the basis; so I asked and found out that they were touting it's "holding up well" after 1 tank of propane; so probably 12 hours of use; or for me 1 weekend. or about 2 heat/cool cycles.  I do not feel that this is long enough a time to make a judgement call on it.  Sort of like jumping off a tall building and saying there are no problems as you pass the 20th floor.  There are ways of posting data to deal with short term testing results; it's as easy as saying "I've used this with my forge for 12 hours so far and have not seen any issues"  (though the number of heating/cooling cycles would make a difference too.)  How would you evaluate that information as compared with "we've been using it in a bunch of forges for 20 years so far and have had great results"?

When I had my surgery earlier this year I researched the surgeon and found he had done thousands of similar surgeries over the last 30 years and was known for having good results. I did not go just by his opinion of his skills.  That's just me.

If my manner is abhorrent to you there is an ignore list you can add me to in your profile and never see any of my posts again. Please feel free as it doesn't hurt me to be on someone's ignore list.

 

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What; you mean I spent all this time being cautious around you (just because you know what you are doing) when there was such an easy way to hide my head in the sand? :)

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Don't worry I won't sneak up on you---(I have GRANDKIDS to do that!)

And I've done a lot of odd things and experiments smithing back before there was easy access to this sort of information.  I don't feel everyone should have to repeat some of the lessons I've had; though cataloging the scars on my hands has kept me awake in some boring meetings...

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missing hunks and crushed chunks are a subject I no longer want to pursue...I have too many of my own, and way too many memories of others I've seen in friends and strangers.

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I plan to make a sheet metal shell for the forge to try and extend the life of the bricks. I was wondering if coating them in with a clay slip would hold them together longer but it sounds like it would not. I will stick with the classic steel box with 2 bricks for now. 

Thanks everyone for the input. 

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On 10/13/2017 at 4:05 PM, ThomasPowers said:

Don't worry I won't sneak up on you---(I have GRANDKIDS to do that!)

And I've done a lot of odd things and experiments smithing back before there was easy access to this sort of information.  I don't feel everyone should have to repeat some of the lessons I've had; though cataloging the scars on my hands has kept me awake in some boring meetings...

Thought I was the only one to catalog scars on my hands & arms in meetings. Since retiring I do it less now.^_^

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8 hours ago, Irondragon Forge & Clay said:

Thought I was the only one to catalog scars on my hands & arms in meetings. Since retiring I do it less now.^_^

I like to brag about my lack of scars. . . well used to, the dents in my head are pretty visible. When I was drilling there'd be the occasional driller work shop. We'd gather for the after party at the hotel watering hole and swap the important stuff. Skilled craftsmen speaking among themselves without the brass needing to express their opinions and needing explanations exchange a LOT more good information tips, tricks, etc. While enjoying the after party I started noticing how many of the guys were missing fingers so I started keeping track. There weren't very many there with as many years as I with all 10 fingers. At that time I'd only been drilling about 10 years.

Frosty The Lucky.

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