Forges 101

[Charles R. Stevens]

You can always cut down the barrel, cut the back third off, cut off the front lip and an inch or two of barrel and press the two to gether. Insulate and now you have a forge and a heat treat oven. Bonus you won't freeze bottles as fast, burning threw money so fast and have the DEA showing up thinking you have a meth lab do to having a dozen 20# cans (don't ask))

 

[Mberghorn]

18 hours ago, Buzzkill said:

It sounds like you are in the typical "it's better to have it and not need it than need it and not have it" mindset as far as forge interior goes.  Been there done that.  You already have a very large forge built, so if you are going to build another this might be the time to see how small you can go and still fit your needs.  Believe me, there is a big difference in propane consumption to keep the one you have already built at temperature compared to a disposable helium or freon canister forge.  If you're mainly interested in forging straight blades, whether knives or swords, it's a good size to work with.  A mousehole in the back lets you heat enough material to work by hand without constantly heating portions that you can't work in one session anyway.  That size gives you about 5 inches internal diameter to work with, which tends to be more than enough for straight blades.  Obviously for war axes or odd shaped blades you'll need the larger forge or other options.  One way to make a smaller forge and still allow for larger pieces is a clamshell type of design.

Anyway, good luck with whatever you choose to do.  I'm looking forward to see your creations.

 

I've come to the same conclusion after reading the info in these pages. I personally don't have any one goal as far as what I want to make. I just like making stuff and learning how to make new things. My fix is the crafting, not the purpose for the end product. I take pride in my work but it's all about the "build" for me!!! I'll tune this forge to get the best production out of it but I think instead of making another smaller gas forge I might just stick with a new coal forge. I'll go through the redesign of the gas forge when it needs to be recoated, and I'll be sure to post updates of the build, but for now I think instead of making all that backwards progress I'll just get what I can out of what I have and make a coal forge for the smaller, more common items.

18 hours ago, Charles R. Stevens said:

You can always cut down the barrel, cut the back third off, cut off the front lip and an inch or two of barrel and press the two to gether. Insulate and now you have a forge and a heat treat oven. Bonus you won't freeze bottles as fast, burning threw money so fast and have the DEA showing up thinking you have a meth lab do to having a dozen 20# cans (don't ask))

 

I feel like you are speaking from experience here.....

[Mikey98118]

There is one problem with mini-forges; they are addicting...

[Mberghorn]

11 hours ago, Mikey98118 said:

There is one problem with mini-forges; they are addicting...

I'm starting to see that first hand, lol!

[Mberghorn]

Back to the rigidizing with colloidal silica.....if I buy fumed silica in a 1 lb bag, can I mix it with regular water or does it have to be demineralized or deionized water? Also what is the mixing ratio?

[Mikey98118]

The only difference tap water is going to make is the amount of mineral content it can leave behind when you get through heating up the ceramic wool to set the silica permanently in place; it won't interfere with the capillary action that places the silica where it needs to go; nor will it effect its performance when in place. Is it possible that a high enough mineral content could affect the ceramic properties of the fiber blanket? The amount of "contaminants" would have to be so high that the water would not qualify as drinkable.

 

[Mberghorn]

On 3/8/2017 at 6:55 PM, Mikey98118 said:

quote removed

Awesome, thanks! I just need to mix enough silica with the water so that it all stays in solution right? i.e. no amount is too much as long as it's not settling out?

[WoodnMetalGuy]

Mberghorn - At this page: http://www.sheffield-pottery.com/KAOWOOL-THERMAL-CERAMICS-RIGIDIZER-p/tcr.htm, I found this information:

Physical Properties

Color clear
Solid content, % silica (approx) 28 - 29
Weight per gallon, lb (kg) (approx) 10 (4.5)
Nominal density, (wet), pcf (kg/m3) (approx) 75 (1202)
Maximum temperature rating, °F (°C) 2300 (1260)
Freezing temperature, °F (°C) 28 (-2)
Viscosity, centipoises @ 25°C 4
Specific gravity @ 25°C 1.203
pH 9.7

So, since water is about 8.3 lbs/gallon, looks like they've got about 1.7 lbs of silica in there.

I mix colloidal silica with epoxy as a thickener in my boatbuilding projects, and that stuff is almost weightless - it would take a bunch of it to make 1.7 lbs.  And it's nasty to mix, floating off into the air with little encouragement.

Overall, it may be better to just buy the pre-mixed rigidizer.  My only concern is that at this time in this part of the country, I'm worried about it freezing in transit, which is something that's best to not happen for some reason.  I may have to wait a bit before ordering mine.

I'm also confused about why this stuff would have a shelf life.  I would have thought it would be good indefinitely.  Anyone know?

Also, I wonder what the coverage is for a product like this?  I'm sure I would need less than a gallon. Calculating inside area, less the shelf, plus the ends, I expect to need to cover about 3.5 sq feet.

-- Dave

[Frosty]

About buying premixed colloidal silica rigidizer. It has a limited shelf life, once you open it it's only going to stay in solution a week, maybe a month before it starts setting(?) up.

Have everything planned out and ready to go. It also needs to be heat set so have the forge and burners ready to light BEFORE you open a bucket. Pre dampen the blanket, apply the rigidizer allow to dry then fire it to red in the forge. Spray with water, apply another coat of rigidizer to the installed layer AND the contact surface of next one  going in. It works well to glue the two together but not inseparably. Dampen this layer, apply a coat of rigidier allow to dry and fire.

Dampen and apply another layer of rigidizer to the blanket just before you apply the hard refractory inner liner so it sticks better. 

Of course that's just how I do it.

Frosty The Lucky.

[WoodnMetalGuy]

Found an answer for the coverage question at this site: http://skylinecomponents.com/CeramicFiberRigidizer.html

So if brushing on covers 35 sq feet, I would only need 1/10 of a gallon...

-- Dave

 

2 minutes ago, Frosty said:

Spray with water, apply another coat of rigidizer to the installed layer AND the contact surface of next one  going in.

Interesting, Frosty.  I hadn't considered that it could be used between layers to glue them together, I was thinking this would just be needed on the innermost face to provide a firmer surface for a thin refractory coating.  -- Dave

[Frosty]

I spend time talking to the guys I but refractories from, even the guys at the sales desks are big into fire and appliance containing fire. Great guys, I've learned stuff every time I go by. It was their advice to use it to stick layers together. It's sort of like adding a capfull of Elmer's white glue to a bucket of water you're using to mix mortar and again to the water you use to butter the masonry before setting it.

I tried adding a quantity of rigidizer to the water I mixed my Kast-O-Lite-30 but didn't notice any difference. I can't think of the name of the fellow a past member here who used rigidizer as the cement to apply zirconium as a kiln wash. I have questions about using a silicate in an environment I was going to subject to borax based welding fluxes. HOT borax just loves to put silicates into solution. Dissolves the stuff just like it does to soft fire brick.

Frosty The Lucky.

[Mberghorn]

On 3/9/2017 at 2:12 PM, Frosty said:

About buying premixed colloidal silica rigidizer. It has a limited shelf life, once you open it it's only going to stay in solution a week, maybe a month before it starts setting(?) up

Thanks for the process, Frosty! I wouldn't have thought to pre-dampen the blanket with water before applying the rigidizer. Would it do any good to apply more than one coat with firing in between? Particularly because I have 2" blanket in my forge. 

WoodnMetalGuy, thanks for the research! You saved me a bunch of time and headache.

[Frosty]

You're welcome. I  just read the instructions on the bucket of rigidizer for final confirmation and buttering the blanket has been talked about for as long as I've been hanging on metal work lists and fora. Wetting the blanket or any surface you're applying a product that dries or hydrolizes like concrete or mortar is standard practice, It's called buttering the joint. It prevents the product from flash drying on contact leaving a layer of powder between the bricks or whatever for no bond. Watch a mason laying blocks sometime, he has a bucket of milky looking water and a paint brush. Wet the wall, lay the mortar, dip the brick and set it.

Wetting the blanket lets it flow along the fibers and penetrate surfaces. There's no problem applying more coats just bear in mind the blanket insulates primarily be retaining dead air space so you don't want to turn it into a solid block. Heck if you want you could dip it and wring it out. I wouldn't but you never know.

Frosty The Lucky.

[Mberghorn]

On 3/11/2017 at 3:49 PM, Frosty said:

quote removed

I haven't gotten my silica in the mail yet so I can't read the instructions. Now I at least have a good idea of what I need to do while I'm waiting on the rest of my materials. Masonry is about the only thing that I haven't tried my hand at so far so I'm glad you gave that example too. It really helps to understand the "whys" behind the methods as opposed to just the "hows". That statement also goes for how the blanket insulates; I didn't know that it was more or less the air in the blanket that does the bulk of the insulating. Ya learn something new every day right?

[Mikey98118]

If you are working with ceramic board, brick, mortar or other surface, pre-whetting can't hurt. Bought sense I've always spritzed the silica based rigidizer into ceramic blanket, I have never used it.

[iamjoe]

My forge build. It has a lot of room for improvement but it's more than what I had.

20170213_200559.mp4

20170213_204531.mp4

[Mikey98118]

  Insulation thickness

Recently someone decided to use 3" of insulation in a small forge's wall, instead of the recommended 2". We all tend to automatically think "more ease better." Me too; but we need to think of consequences. Here, it is the need to keep the amount of super-heated insulation, that is very close to the burner, severely limited. How limited? How much insulation do we want to use? if more insulation is better, it needs to be balanced with more limitation  to heat gain in the burner's mixing tube as an inevitable consequence; that means that, in the area of the burner, a recess area in the forge wall become necessary, to keep the amount of burner port tubing that is exposed to the forge wall's incandescent insulation. And how to we come up with the wanted recess? Look to kitchen funnels, etc.

[Mikey98118]

BTW, that is a nice hot forge.

[Irondragon Forge ClayWorks]

I am at the point of installing 2 1 inch layers of Kaowool. Planning to use Frosty's rigidizer  of 30 % Kaolin/ 70% kiln wash. My question is are the measurements by weight or volume?

[Mikey98118]

I'm sure that was just a "slip of the tongue". Frosty's kiln wash is meant to provide, or supplement a finish coat over ceramic wool insulation; not to rigidize it.

That said, I have been noticing a lot of newbies confusing finish coats and rigidizer functions lately, as though use of the two products amount to an either or choice, rather than two interlocking construction steps, which end up supporting each other. One of the things a finish coat is meant to do is seal the insulation; preventing it from becoming air-born, and entering people's lungs. Rigidizing the wool will not stops this from happening.

I have seen some newbies assuring others that a good finish coat makes rigidizer unnecessary. There is no such thing a cheap finish coat. On the other hand there is no such thing as an expensive rigidizer. Ceramic wool shrinks from exposure to high heat. One of the things a good finish coat does is to deflect some of that heat away from the wool. Finish coats crack and even pop away from the wool in chucks due to physical damage and from shrinkage of the wool; rigidizer fights both of those problems.

We are all given two legs two stand on; maybe the geniuses who think who think finish coats trump rigidizer should try standing on just one of theirs for a while, and reconsider that idea.

[Irondragon Forge ClayWorks]

My wife is the potter of the family and understands all that stuff about kilns, kiln washes, rigidizer's, clay properties, Satanite, Kaowool, and on and on. Stuff that's over my head or goes in one ear and out the other. The solution we came up with is she will be in charge of what goes inside of the forge and I for what goes on the outside.

[Mikey98118]

Very smart choice fella

Probably I would enjoy shop talk with her. I think potters, like warm glass artists, need to know quite a lot.

[Frosty]

4 hours ago, Irondragon Forge & Clay said:

My wife is the potter of the family and understands all that stuff about kilns, kiln washes, rigidizer's, clay properties, Satanite, Kaowool, and on and on. Stuff that's over my head or goes in one ear and out the other. The solution we came up with is she will be in charge of what goes inside of the forge and I for what goes on the outside.

Ditto Mike, GOOD choice! Let the expert do his/er thing and help of possible but mostly stay out of the way. Can you talk her into subbing to Iforge? I'd LOVE to pick her skill sets, What I know about building furnaces is from experimentation and reading kiln books. 

A forge has some different desired characteristics than a kiln or glory hole but at heart they share the same principles.

Tell her Frosty says please. 

[Mberghorn]

I have one last question about rigidizer. How much needs to be applied? Obviously it depends on the inside surface area of my blanket but is it possible to oversaturate the blanket? I'll be spraying it on so I don't want to go spritzing a whole quart when only a pint will do.

Frosty, is your finish coat recipe by weight or by volume? I might have missed it in the earlier comments but seeing Irondragon's post the other day reminded me.

[Mikey98118]

Yes, it is possible to over saturate the blanket, but all that happens then is that the excess mixture coats the inner side of your forge shell; no harm done. I think most people don't get what a small amount of glass is actually contained in colloidal silica contents; in a gallon jug of fumed silica doesn't way as much as the plastic container it comes in.Yet, glass is HEAVY; to  swim in water without settling to a container bottom the silica particles have to be very small.

The magic of colloidal silica ( fumed silica in water) comes from capillary action. The silica and water mixture isn't running down the ceramic wool fibers due to gravity, but due to whetting action; each time some of it reaches an intersection, where two or more fibers meet, some of it stays in the intersection because surface tension balances the capillary force running along each fiber, allowing a tiny glob of silica to build up until no more of the material can be supported in the joint, and all further silica and water flow on by it.

Next, you dry out the water content, and the silica powder is melted to glass by the burner  before it can drop off the fiber. The build up of material is so small it would take a micrometer to measure the increase in the diameter of individual fibers, except at the intersections where much more silica collected...fortunately.

I recommend that people making their own rgidizer add food coloring (for a temporary dye), as most suppliers do, so that they can see how far into the ceramic wool the colloidal silica has penetrated. After firing, the food coloring is burned away, and the wool appears white again. Do you need the dye to due the work? No, but it goes a long way toward quieting anxiety

I recommend doing some reading about capillary action, whetting, and surface tension by doing a little research on the web; just input "brazing" to get a reasonably quick education on the subject.