A few questions before I start building my propane tank forge

[Fallon]

I'm in the process of making my first gas forge. I inherited a brake drum coal forge somewhat recently. It's fun, but Coal is a pain & brake drum forges aren't a great design. So I've started chopping up an old propane tank with an obsolete valve to make a propane tank propane forge. I've done a pile of research here and, on various other forums & been pretty depressed watching some of the hacks do stupid things making poorly designed or dangerously implemented things on YouTube. I have a couple questions to try & make my first gas forge build successfully.

Is it better to rigidize the blanket then install it before it dries or to install it then try to coat it evenly?
Do you need to fire the first layer of rigidizer & blanket before you put in the 2nd layer of blanket and again before you coat it in refectory?
Do you need to fire the refectory before you coat it in IR reflector?
How long does dry Kast-O-Lite 30 last if you put it in a good sealed bucket? Similar to concrete, indefinitely if you keep it sealed & dry?

I cut off the front of the tank to clean it & properly install stuff. I'm a hack welder but have a TIG/stick machine & some little ability. Should I try & weld it back up after assembly or put on a hinge? If I hinge it, how do people handle the edge? Cover the ceramic blanket with refectory all the way to the shell? Leave it mostly bare ridged blanket? Are there issues with the blanket or refectory not creating a good enough seal to protect the shell? Would I be better off just not putting front on & leaving it refectory covered blanket? I have a really nice powered respirator to wear when building things, before it's rigidized.

How big of an opening do you put on the front? Wayne Coe's pictures & others have a D shaped opening around 1/3 of the front of the propane tank. I know some of that is subjective, but a aware of potential backpressure issues as well. Most of my work will be knives, maybe up to manchette size, probably along with tongs & other shop or blacksmithing tools. I'm guessing the propane tank forge is a bit big for some of that, but I'm hoping it's not to inefficient. Would I gain much going with 3" of blanket for extra insulation & to decrease volume? I've seen plenty of debates on pointing the burners straight down or in at an angle & haven't figured out which school of thought I'm going to follow. Both seem to be valid, just different use cases & trade offs.

For the floor, do people go with round or flat? If flat, do you just build it up with rigidized blanket then coat with refectory? Would soft or hard fire bricks be a better choice to build up & level? Would coating the bricks in refectory cause thermal expansion cracking issues? I'm assuming I don't want a really thick refectory floor beyond 1/4-1/2" or so to avoid being a large mass to heat up.

I've got a box of 1" 8PCF ceramic fiber spun blanket, rigidizer, box of Kast-O-Lite 30, some ITC 100 (should have gotten cheaper stuff I now realize), high pressure regulator & a pair of Black Beauty burners. Scrounged up the parts over the past while off my scrap pile, local farrier, Internet & Craigslist. I have intent to make a furnace for some aluminum casting at some point too, so extra blanket & refectory will get used. I hear the rigidizer doesn't last long if mixed, so only going to mix up the minimum needed & store the rest.

It's winter here in Colorado, so I assume all rigidizing, refectory & ITC 100 installation & cure time will be in the basement rather than the unheated shop. Will lug things out to the driveway to fire.

 

[MaxwellB]

34 minutes ago, Fallon said:

Is it better to rigidize the blanket then install it before it dries or to install it then try to coat it evenly?
Do you need to fire the first layer of rigidizer & blanket before you put in the 2nd layer of blanket and again before you coat it in refectory?
Do you need to fire the refectory before you coat it in IR reflector?
How long does dry Kast-O-Lite 30 last if you put it in a good sealed bucket? Similar to concrete, indefinitely if you keep it sealed & dry?

1 & 2 - You don't need to rigidize the first layer if you're doubling up. Only the fire-facing side needs to be ridigized, and since you're looking to put a refractory on top, you don't absolutely have to rigidize at all. It will make the refractory process easier, but for sake of uniformity with other advice, no... Just rigidize the top most layer.

3 - Yes. Your refractory should be completely cured before you apply the IR. You will want to repair any cracks that form during the cure and make sure your refractory is 100% ready to go before applying IR.

4 - KOL doesn't dry. It cures. It acts like cement, where the water creates a chemical reaction within the refractory and triggers the curing process. If you're thinking of mixing up 20lbs of KOL and trying to save the rest, you'll end up with a bucketful of solid stuff. Any excess you have after you coat the walls you could use to build sacrificial plates to put on the floor of the forge, as that will take the most abuse from stock poking and flux and other nasties.

[Mikey98118]

7 minutes ago, Fallon said:

Is it better to rigidize the blanket then install it before it dries or to install it then try to coat it evenly?
Do you need to fire the first layer of rigidizer & blanket before you put in the 2nd layer of blanket and again before you coat it in refectory?
Do you need to fire the refectory before you coat it in IR reflector?
How long does dry Kast-O-Lite 30 last if you put it in a good sealed bucket? Similar to concrete, indefinitely if you keep it sealed & dry?

If you don't mind dealing with a  dripping mess, and wasting rigidizer, go right ahead on. I prefer to add a little food coloring to the solution and get a perfect view of when the rigidizer has soaked into  each layer of blanket. I also prefer to heat cure the first layer to stiffen it before putting the second layer into the forge. What people don't realize is how perfectly the rigidizer runs along the individual fiber surfaces, being pulled ahead by capillary action.

Yes. you need to fire the refractory before aplying any coating to it.

Even sealed refractory has a shelf life, but I have used it six months layer and observed no difference.

23 minutes ago, Fallon said:

cut off the front of the tank to clean it & properly install stuff. I'm a hack welder but have a TIG/stick machine & some little ability. Should I try & weld it back up after assembly or put on a hinge? If I hinge it, how do people handle the edge? Cover the ceramic blanket with refectory all the way to the shell? Leave it mostly bare ridged blanket? Are there issues with the blanket or refectory not creating a good enough seal to protect the shell? Would I be better off just not putting front on & leaving it refectory covered blanket? I have a really nice powered respirator to wear when building things, before it's rigidized.

Go for a hinge , and add a  latch on the opposite side of the door. Leave the insulation snort of the openings on both cylinder and end piece; finish each of them with a layer of Kast=O=ite. and use a straght edge to scrape the drying excess material off.

 

32 minutes ago, Fallon said:

How big of an opening do you put on the front? Wayne Coe's pictures & others have a D shaped opening around 1/3 of the front of the propane tank. I know some of that is subjective, but a aware of potential backpressure issues as well. Most of my work will be knives, maybe up to manchette size, probably along with tongs & other shop or blacksmithing tools. I'm guessing the propane tank forge is a bit big for some of that, but I'm hoping it's not to inefficient. Would I gain much going with 3" of blanket for extra insulation & to decrease volume? I've seen plenty of debates on pointing the burners straight down or in at an angle & haven't figured out which school of thought I'm going to follow. Both seem to be valid, just different use cases & trade offs.

The best opening size is--wait for it--variable; as in build it too large, and then use bricks. etc. for a baffle wall in front of the opening.

You will be happier staying with 2" of blanket. Burner positioned at one o;clock and aimed at near edge, or three o;clock and aimed at far edge of floor.

[ThomasPowers]

Re welding the front back on:  remember that the liner is a consumable and will have to be replaced; *much* easier if you can remove the front easily. Or just tack weld so it's easy to cut them when needed.