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Small Gas Forges


Alan DuBoff

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Hi Alan.

Got back from a day at the park with the wife and kids, on the way home we stopped at a big home center out in Tachikawa. I got some fire bricks, the cheap yellow type, they are rated to 1500C they say, about $1.50 each, at least I could get them!

I picked up a large charcoal brazier for just under $10, and this is what I did.....

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There is sits, $10 worth of charcoal brazier

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Unwrapped.

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Ready to go!

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12 x $1.50= $18 worth of fire bricks

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It is about 15cm wide (6")

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...and 19cm deep (7.5")

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I got rid of the three little nubs on the top, so the fire bricks would make a better seal up front. Here I just stuck one of my torches in the air hole to see how it worked, and it did not work great, the torch was not very stable, did not like that much, so I drilled a hole in the side of the charcoal brazier, actually two holes....

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Here is how I stack the bricks in front, I can make the hole in front bigger or smaller with ease

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In use....

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Here you can see the torch stuck into the hole.

Continued in the next post.........

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........... OK, I got it fired up and fooled around with it....

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Lights off hot steel pics

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more

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Yet more

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Looking in the air-hole with the lights off

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Looking in the air hole with the lights on....

Conclusion? Well, I think I need more heat. The two torches just don't put out enough heat for the space. I think the charcoal brazier did just fine for containing the heat, as the outside of the unit was hot, but not REALLY hot, a gloved hand did not have any problem with touching or moving it around while still hot.

I guess I have to work on some formulas here to figure out how much heat I need.

The volume is about 212 cubic inches, so what kind of heat source do I need?

I found that by opening up the front hole and the air hole on the back things seemed to run hotter, but I've only got the iron heating in the forge to judge that.

I'll be going to a place I can buy a 20lbs propane take and some other bits tomorrow, so I hope I can get this going better.


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BTW, this is the chunk of rail I have as an anvil

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And this is my exhaust fan in the Dungeon it is rated at 650 cubic meters per hour, so it really does suck :D

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Go Stu go.! :D

I think the reason it's not geting hot enough is that there probably is not enough air. Remember that air causes heat with fire, and I read recentely that acetelyne (which propane is NOT) will heat up to about 4000 derees on it's own, but with oxygen it can go to 6000. I hope I'm not pulling these figures out of my you know where, but I remember reading this. The oxygen will allow it to get that much hotter.

The other reason could be the burner tip that is on the propane tank. Remember that you will burn those tips easily when using stock tips from a propane tank like that. But it should get hot enough. You might be using the MIG tips you mentioned.

Score on the firebrick, I need to get some.

I'm waiting on my burner to get here before I futz around with propane, and with some firebrick I can use the portable solid fuel forge I have. It's not clear which will win out in the end, but I am a solid fuel type person, even in my BBQs, I don't use propane of any type.

It's almost getting hot enough for you, it's starting to get red.:o

Maybe someone more knowledgable on propane has some suggestions.

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Okay, this is my second attempt to send a reply to this thread. My first one was several pages of wonderously enlightened information but when I tried to attach the concept drawing I discovered I'd timed out and lost the whole kit and kaboodle!

First off are a few rules of thumb to consider:

How much burner is enough? Most smiths consider enough burner to be one that will bring their forge to welding heat. With decent flux this is in the high yellow. Most people buying a commercial naturally aspirated forge settle for less. A base rule of thumb is derived using a simple linear burner in an uninsulated forge lined with a hard refractory or a brick pile. This rule of thumb is: One, 3/4" burner for every 350 cu/in of volume. This is a good baseline to use regardless of the burner you build or buy. If you insulate or buy/build a higher efficiency burner you'll have a good margin of overkill. Overkill is good; you can always turn it down but you can't go beyond max.

This is often about as far as folk go but there are a number of other factors it doesn't hurt to consider.

What type of burner do you want? I'm not going to go into (blown) "gun burners" here. I have nothing at all against gun burners, I just don't use them so have little to say.

Of the "naturally aspirated" induction devices there are two that are suitable for heating furnaces:

The first type is the "Linear" induction device. Examples of these are the: Bunsen burner, aussie, Reil, etc. The air intake, primary (gas) jet and tube are in a line. (linear arrangement) They can be identified by looking up the bore. Ignoring choke plates, etc. if you can look straight through them it's a linear. A purpose built commercial linear induction device has a max amplification ratio of around 19:1.

The other appropriate induction device is called a "Jet Ejector". Examples of these are: Fisher burners, Mongo, Porter generations 2-4, T Rex, etc. A jet ejector's air intakes are arranged at 90 degrees to the tube and jet. Looking up the bore you'll see the jet and it's mounting but can't see through it. A commercial Jet Ejector can induce up to 29:1.

How choosing the type of inducer you want to adapt for a furnace burner effects things is, Tolerences. A neutral burn, air : propane ratio is 17.5 : 1. If you decide to build a linear you have to do a darned precise job of it, seeing as max induction for a commercial linear is 19 : 1. You just can't afford to lose much efficiency and still expect a good flame. If on the other hand, you decide to build a jet ejector, you can fall well short of the commercial 29 : 1 ratio and still have a super efficient home made burner.

Another consideration is buy or build? Either is a perfectly valid choice depending on your situation and bent. If, like Mike Porter, Ron Reil and myself, to name but three, you enjoy building a piece of equipment as much as using it, you'll really enjoy building your entire smithy from the ground up. If on the other hand you're a "git er done" kind of guy and have the cash, buying is a fine way to go.

I simply can't afford to spend several hundred bucks just for a hot fire. I built my own forge and burners. Not counting time invested I've probably spent under $100 over the last 15 years or so on forges and burners. The little forge I've been using since 95' will melt steel if I turn it up a bit, say 12-13psi.

Ron and Mike have both taken burner making to a high point. They make burners that are precision intense and time consuming. Both make burners that are several percent more efficient than the one I'm going to show you here. This is where Mike, Ron and I differ, I'm basically a minimalist at heart. I like my machinery as simple as will do the job well, I don't need perfection. I also seldom build multipurpose equipment unless it's a natural marriage. A good example is a forge convertable to a melting furnace. This is a good multipurpose device if you're needs are similar enough for the compromise.

The last "T" jet burner I built was summer before last and I spent a whopping $9.00 for parts and almost 20 mins. making it. The following description has been altered to reflect how I made my last burner. (Yep, you guessed it, I have most of this text saved and update it as necessary.)

So, the attached drawing is of the Jet ejector type burner I've been using for the last 10 years or so. I call it the "T" Jet burner and with small refinements I haven't changed the design in 10 years. You'll quickly notice there're no labels, dimensions or other helpful tips. This is why I call it a "concept drawing" if you need more, let me know and I'll do what I can to help. Same for my description, I've tried to do an adequate job of it but some folk need more info. Just let me know.

You will have to spend a little time wandering around a halfway decent plumbing supply for the brass fitting to make up the mig tip and the lamp rod. You'll also have to find lamp rod. Hope you're not overwhelmed yet!

----------------------------------------------

The tube is 1" x 8" black iron pipe.

The "T" is a 1" x 1" x 1" black iron "T".

The "jet" is a 0.045" Miller mig tip. Shortened to 9/16" long and deburred.

The jet attaches to the 1/8" SPT (Straight Pipe Thread) lamp rod via a 1/8"
FPT brass fitting or cap, drilled and tapped 1/4"-28. Get lamp rod at Fred
Meyer's, etc. in the lamp repair section, get one or two lock nuts too. If
you go to an electrical supply or hardware store it'll cost twice or more
as a dept store. On the other hand it's only a buck or two per foot at most,
anyway.

You can eyeball center when drilling the top of the "T" for the lamp rod but the
better the alignment of the jet down the center of the tube the better it will work. This alignment is the single most important factor to making a good tuneable burner. Screw the
tube and "T" together make match marks and chuck it up in the lathe to drill and
tap for best alignment. After drilling the hole, chuck the 1/8" TPT tap in the tailstock or drill press chuck and hand crank to tap the threads. This will keep them as perfectly aligned as possible.

If you don't have access to a lathe you can use a drill press but will need to make a vertical "V" block to align the tube and all the rest. Use a piece of large 1/4" x 2"+ angle iron as the base plate and weld two smaller pieces, say 1" angle parallel and square to the base. The idea is to clamp the vertical "V" block to the edge of the drill table with the parallel "V" hanging over the edge. The "V" needs to be as perfectly aligned to the drill press chuck as possible. Chuck up a long straight piece of round stock, say 1/4" and with the burner tube clamped in the "V" block align the 1/4" straight down the tube. Clamp it solid and you're ready to go.

I don't have a 1/8" SPT tap so I use 1/8" TPT (Tapered Pipe Thread. I can't
recall what it's properly called right now) and thread the hole a little at
a time till the lamp rod just threads through it. If you run the tapered
pipe tap too far you get a lot of slop, you get a little anyway but it's
controllable if you're careful. A little slop is actually helpful for fine tuning the jet's alignment.

Now thread the lamp rod into the "T" without removing the assembly from the
lathe or "V" block and lock it in position with one of the nuts. Install the brass 1/8" FPT x ? fitting on the tube and snug it up. Drill and tap the brass fitting for 1/4"-28. Now screw in the shortened mig tip, insert a 0.045 drill bit shank in as an indicator and spin the lathe to see if it's straight, gently tap the mig tip as needed till the tip is straight.

If you're using a drill press, remove the lamp rod and gently chuck it in the drill press. Insert the 0.045" drill bit shank into the mig tip and hand crank the drill press. Watch for any wobble and correct it with gentle taps of a hammer. Be careful or you'll damage the lamprod threads.

Once you have the lamp rod and mig tip aligned thread it into the hole in the top of the "T" from inside. Bring the brass fitting all the way to the "T" and lock it down with a nut from the outside. Using pipe tape or teflon paste, attach your hose fitting and you're ready to test fire it.

I wouldn't really call these a "project" they take me maybe 15 minutes to
make with my lathe, 20 if I don't turn it on and hand crank it.

I also don't put tapered flares on them, I only run them in the forge and they
work just fine. To be fair, they will not burn open air. If you have use for an open air torch then adding the flare and doing the trial and error work to tune it will be worth the effort.

A proper flare is a 1:12 ratio or a 2.5 degree taper.

Now, let's see if I can get the drawing attached and this sent without losing it.

Frosty
-------------------------------
If it ain't forged
it ain't real.
Wrought iron is.
The FrostWorks

Meadow Lakes, AK.

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Stu:

You don't have nearly enough burner for the volume you have. Butane and even mapp gas torches work wonderfully well in bean can forges with less than 10 cu/in.

You need to build or buy a proper burner.

What really catches my however is the charcoal braisure you're using. It looks pretty well adapted for a different type propane forge I've been toying with. they're called "chip forges".

Basically a chip forge is a bed of refractory chips laying on a grate with air ; propane forced up through them. They heat like coals and once hot there is little or no exposed flame.

Chip forges or hearths are big in europe and are typically gun burners. I and a couple other folk are playing with making them work with naturally aspirated burners. An experiment last summer melted 3,000f refractory kiln shelf. Yes, MELTED it. :o

Frosty

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Is that weeny dog? He/She is cute.


That's Pocket, she's half miniature daschund and half chihuahua and a 7lb. sweetheart. She's there for scale instead of a. . . Scale.:rolleyes:

Attached is a pic I was looking for to show the "T" jet burner I made summer before last in action. I made it as a gift for the host of a little annual get together.

Unfortunately the glare from the forge makes it hard to see the burner but it's poked through the near sidewall. Rich had owned this particular 2 burner forge, A Whisper Moma I think, for a number of years and could never get it much hotter than high orange.

As you can see it's well into welding range. Rich ended up having to redesign his table. As it used to be he had the bench top level with and right against the bottom of the forge door which was really handy. About half an hour into the forging session with my burner the wood under the steel top caught fire.

We didn't stop of course, other than to pull the smoldering drawer out and start regularly dousing the underside of the bench with water.

Frosty

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Frosty,

I agree you can build a darn good burner cheap, and you've shown just that. Most everything I've read about the better burners is that they're worth it. I've talked with several folks that have built their own burners and never got near the results that they do with a T-Rex or similar. Not that everyone needs that welding heat, but most want it if they have a forge.

I'm seen cautions and warnings about CO leakage in these forges, but a friend of mine says that it's so small it's not worth worrying about. What to make out of that?

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Frosty, what can I say, thank you very much for the info!

While I was out at Joyful Honda my DIY heaven, I checked this site and this thread via my cell phone, and found the info you put up. A lot to read on a little cell screen but I did, and I even saw the pics and such.

I bought some stuff and cobbled together a burner, it did not work well...... :(

But I'll get some more time tonight and I hope to improve it.

I got a 8kg propane tank and a regulator for just under $100 here, and filled it for another $15, should be enough gas to keep me going for a while.

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here is the burner I made..........

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The tip in there is a Mig tip, a #35, I guess that is too small, as I could not keep a flame going without covering most of the air inlet holes (with duct tape). With the pressure on just a smidge above zero too.

I guess I need to make the hole bigger, you recommend a #45, and also I guess I need to put the tip further into the burn tube...?

The pipe and fitting is all 3/4", I bought some 1" as well, so I'll try both.

I did not find any lamp rod, so I was thinking of drilling a section of ready rod, on the lathe (It is a wood lathe, but I have a good chuch and a drill chuck for it too). I'll then drill everything else like you say in your great post above.

Wish me luck!

Cheers!

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I think you need to extend the mig tip a bit more down into the tubing, as well as increasing the pressure, not too much, but a little above zero seems like NO burner would run on that. Did you make a flare tip for your burner too? You could also make some little sliding doors to cover the air inlets, so you can adjust the amount of air as you increase the pressure of gas.

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Stu:

You work FAST brother! :D

The directions I sent are for a 1" burner, scale everything down for a 3/4". Make the tube 6-7" long. The correct ratio is: tube L = 8-9 x bore dia.

Use a 0.30" mig tip for a 3/4" tube and move it back away from the bore not into the tube.

You should be using black iron pipe at least for the burner tube. The galvy will burn off and is hazardous. Zinc smoke isn't the extreme danger most folk think but it will make you sick and there's no point in exposing yourself unnecessarily.

There are also hazards associated with propane in contact with zinc but you aren't keeping the two in close contact for any length of time. Unless the hose barb is galvanized, then you should replace it with a brass one.

Don't worry about teflon tape where the "T" and tube connect.

Yes, using all thread or simply threading some 1/2" mild steel rd. is actually better than using lamp rod. I didn't mention it because most people don't have a lathe and I wanted to hold the post length down. Some. :rolleyes:

Good job Stu.

Frosty

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something I'm sure you've been made aware of, but thought i'd include it on the off chance you haven't. Forge and Burner Design Page #1
Even with the ventilation, it would be nice to know what you've got to breathe.

Http://www.kidde.com is the new link location


I have carbon dioxide and carbon monoxide detectors in the Dungeon, thanks for the concern.:)
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OK Pics.

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The new and improved burner!!!
Like I said, using the 1" pipe, I drilled the hole in the ready rod, tapped it for the MIG tip, drilled the MIG tip out to 0.046 and I shaped the MIG tip to a more pointy shape.

At first I had it further into the tube, but then I backed it off and in this spot it worked well, consistant flame, seemed to be burning neutral to my eye.

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OK this is the start, burning well, reg set at 0.02 MPa which is about 2.9PSI

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One minute later

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Two minutes later

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That thin little metal air door is not going to last

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The air door shut, and glowing red!

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Reg at 0.02 MPa (2.9 PSI)

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Cranked the reg up to 0.04 MPa (5.8 PSI)
Six minutes have gone by.

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Hot stuff, and fast!

Boy did that heat up in a hurry. that bar is mild steel, it is 19mm or about 3/4" thick, the red part was about 8" long, and that happened in a jiffy.

Man am I impressed :D ............................. cont............

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............. the aftermath..........:rolleyes:

The charcoal brazier is not going to last, only cost $10 or so, thus I'm not worried or upset, but it is just NOT going to last :D

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Cracks here.........

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..........Cracks there.........

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..........Cracks just about everywhere.............

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............ LOTS of cracks in here! :rolleyes:

Oh well, I'll just have to build a better one, but this $10 charcoal brazier sure got me started

I found the white (Expensive!!) fire bricks at Joyful, about $6.50 each, so if I cannot find the ceramic matting stuff, I'll build a square forge using those bricks.

Hot stuff, thanks everyone for the help!

Cheers!:D

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Did you use a #46 drill or a drill sized for .046 inches? A #46 drill give a .0810 inch hole which is way too big for a 1 inch t-burner. I think a #56 or #55 drill would be closer to what you need.


Sorry Dave, I drilled to 0.046" I thought it might be small, but I figured if it was, I could go up one size, if I drilled it too big, I'd have to use a new tip.

Cheers!
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Well done Stu! Your bar looks weldable with a little brushing and some borax. Keep it adjusted so you have a little dragon's breath coming from the door and you won't get oxidation in the forge. You will get CO instead regardless, so keep the exhaust turned on and a door or window cracked! CO monitor!

You're a delightful combination of build it yourself and "git er done" kind of guy. You are going to make one heck of a blacksmith and bladesmith.

I have one comment about your "dungeon". I hope it isn't in a basement. If it is Please PLEASE store your propane cylinder outside when you're not using it and keep the exhaust going and a window or door cracked when you are. I know I've said it before but I'll say it again and without apology!

Propane is heavier than air and WILL settle in low spots making explosive pools of air/gas just waiting for a spark to blow you to Kyoto.

Please be very careful. Propane works well and is an easy, minimum maint fire to learn with but it is hazardous. All fire is but propane can be especially dangerous to you and others. Think CO and oxy depletion under normal use and explosion potential when shut down. :o

Just be careful okay? I don't have so many friends I can afford to lose one to something avoidable.

Play hard, play safe. Be :cool:

Frosty

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Looks great, now try using the fire bricks as the whole firepot chamber setup, that might work better.
Actually that's true.

Seems that's a common style, using bricks to form the forge. I guess for the most part I would be doing the same by building a firepot of such on my solid fuel forge. The difference being that I don't have to worry about air if using some type of atmospheric forge (worry in the sense of providing it).
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Well done Stu! Your bar looks weldable with a little brushing and some borax. Keep it adjusted so you have a little dragon's breath coming from the door and you won't get oxidation in the forge. You will get CO instead regardless, so keep the exhaust turned on and a door or window cracked! CO monitor!

You're a delightful combination of build it yourself and "git er done" kind of guy. You are going to make one heck of a blacksmith and bladesmith.

I have one comment about your "dungeon". I hope it isn't in a basement. If it is Please PLEASE store your propane cylinder outside when you're not using it and keep the exhaust going and a window or door cracked when you are. I know I've said it before but I'll say it again and without apology!

Propane is heavier than air and WILL settle in low spots making explosive pools of air/gas just waiting for a spark to blow you to Kyoto.

Please be very careful. Propane works well and is an easy, minimum maint fire to learn with but it is hazardous. All fire is but propane can be especially dangerous to you and others. Think CO and oxy depletion under normal use and explosion potential when shut down. :o

Just be careful okay? I don't have so many friends I can afford to lose one to something avoidable.

Play hard, play safe. Be :cool:

Frosty


Right you are Frosty, the propane cylinder will be stored up stairs, out of the Dungeon, yes it is a basement.

Thanks for the kudos, I'm just starting here, but I like to make it myself, so we will see how this goes.

Now on to a more permanent forge, I want a fairly small unit that I can move around, like the size of a lunchbox planer (space is ALWAYS a problem for me!) I'm thinking some of the white bricks, arranged in a box like formation, with angle iron as a frame, then covered with sheet metal to make a box, door in the front and back?

Need to find some more designs on a square, or box forge.....

Cheers!
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While I'm at it, I saw three different kinds of fire brick, not counting the yellow BBQ bricks I already have.

They were all white, two were more of a cream color:rolleyes: They were all the same size, one said B5 one said B6, these were the same price, about $3 each and the third one had no markings, but was a much whiter white, and was $6.50 each.

I'm assuming that the white white one at $6.50 was the best one, for insulating qualities, these were over in the kiln section of the crafts dept.

Would it make a difference if I use only the white bricks and not the B5 or B6 bricks? I guess I'll need a dozen or so bricks, so If I do use the cheaper ones, the price will be a lot less (always looking to make my dollar work as hard as possible for me!!) but, if the B5 & B6 bricks are not up to snuff, then I'm wasting money buying them, right?

Design of a brick forge anyone? Layout of the bricks...?

Cheers!

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