new forge build

[Theintegrator]

Another newbie with forge questions.  

Details:

a. 20# propane tank

b. Frosty burner

Questions:

1. does rigidizer = colloidal silica? 

2. how do i apply it? before tucking the kaowool into the tank? Any other tips for applying it? (Frosty mentioned sopping wet kaowool in one post, but i couldn't figure out the context.

3. What's the best angle to set the burner into the tank?

 

I've scoured the archives and found answers to most everything else--Thanks all!! These are the questions that remain.

 

[Mikey98118]

Colloidal silica is the most popular rigidizer used with ceramic blanket insulation; not the only one.

there are two different alumina based rigidizers; one colloidal, and the other not. The colloidal alumina rigidizer ($$$) works in a similar fashion to colloidal silica, but should toughen it up against shrinkage and crystallization aging. Alas, this product costs more than a change of blanket. Non-colloidal alumina rigidizer works very similar to a coating of castable refractory, but gradually thins out as it penetrates deeper into the blanket. The idea being that it is that it is supposed to form a boundary layer between a solid surface coating and the insulating portion of the blanket. But, the reality is; this plan flies in the face of ceramic blankets ability to delaminate in that direction with no trouble at all.

  Spritz it on after tucking the Kaowool into the tank. I don't wet the blanket first, because the rigidizer spreads by capillary action. Wetting solid surfaces before coating them, is smart. On the other hand wetting the blanket first won't hurt anything. Rigidize the blanket in strips, and use the burner to dry, and then cure it; this way gravity is your friend; not your enemy.

The best angle to set the burner into the tank, is from about 2" away from top dead center, and aimed so that the flame will impinge a little way in from the floor's nearest edge; not at it's center.

Use common sense. If you have an extra wide floor, modify the position of the the burner opening so that it is still aimed inward at a tangiest; not outward.

[Frosty]

I mentioned sopping wet blanket as TOO wet. I'm a proponent of buttering anything to which you're going to apply rigidizer, hard refractory, mortar, etc. It's something I learned from masons when I carried hod and mixed mortar. The main purpose is to prevent a dry surface from flash drying a water setting material on contact. If mortar dries on contact with another material the dry mortar will make a barrier preventing proper bonding and also prevents it penetrating surface features. 

This applies to a colloidal rigidizer on ceramic blanket for the same reasons if not so pronounced. Kaowool as actually pretty absorbent as the blanket while individual fibers are not. Applying a rigidizer solution behaves like any fluid subject to capillary action, it's drawn from the wettest to the driest along any contact surface, this is why it flows into cracks faster than along open surfaces. While the rigidizer is flowing the blanket is drawing off moisture and can cause the dry boundary layer. 

A solution is denser than plain water so any solution will displace the water and flow more deeply. On a ceramic blanket this means there is no real boundary layer between rigidized and untreated blanket the treatment fades gradually.

Buttering and spritzing with rigidizer solution before troweling or casting the hard inner liner causes a better bond. Just buttering allows a better bond when applying a plaster grout, cement, mortar, etc. 

Frosty The Lucky.

[Theintegrator]

Thanks guys for the advice; makes sense now. I couldn't've done this without all the experience and knowledge available on this forum. Terrific!

[Mikey98118]

Frosty,

Well, we seem to have traded places on this issue. However, I am all for careful preparation at every stage of a build. So, from know on I will recommend buttering before rigidizing.

But this brings up a separate issue. These days, I recommend drilling a small hole (1/8") in the bottom of the forge shell. The point is to provide a sufficient exit for steam, water vapor, and liquid water, no matter how well sealed the hot face surfaces of the forge ends up.

[blacksmith-450]

20 minutes ago, Mikey98118 said:

But this brings up a separate issue. These days, I recommend drilling a small hole (1/8") in the bottom of the forge shell. The point is to provide a sufficient exit for steam, water vapor, and liquid water, no matter how well sealed the hot face surfaces of the forge ends up.

Good idea.  I'll do that on my new forge.

[Theintegrator]

me too.Thanks again.

[Mikey98118]

From the beginning I designed all my equipment to be built without need of a welding machine, or anything more than hand tools. Nevertheless,  hot water could be seen running out of some forges, after long periods without use. Because wire feed welders are being used in ever more home shops, forge shells are also becoming more water and steam tight, so the time has become ripe for water drain holes

[Frosty]

A weep hole is a good idea, even if you leave plenty of porosity in the liner for steam to escape. Propane generates a LOT of water vapor and a byproduct of combustion and until the forge shell and liner warm above 212f. water WILL condense in them. No you can't realistically make the liner completely water proof. It will continue to steam and dry until 230f. drives off the hygroscopic moisture. 

Soils lab days arise again. 

Did we change opinions about buttering blanket and masonry before laying the next layer? If I ever said otherwise I misspoke. Butter GOOD! Add a few DROPS of Elmer's or equivalent white "milk base" glue to the butter water it makes masonry bond even better. <shhhhh, that's secret stuff you know>

Frosty The Lucky.

[Mikey98118]

No;  we changed apparent positions from my usual stand of  " do everything just so", to your usual position of "good enough is good enough." While that gave me a grin, it wasn't really what was going on.

[WayneCoeArtistBlacksmith]

My dad always said, "If you have to ask, is it good enough, it probably aint. 

Wayne

[Frosty]

It's the same balance you find when a machinist builds a house. You don't really need to measure the rafters to a tolerance in the ten thousandths but habits are hard to break. When we built this house the builder we hired kept trying to compensate for how much he thought I was going to be off on measurements. Finally I cut one to his dimension and it was too long to fit by the 3/16" he compensated.

Fixed that, I over killed the tolerances and measured everything to a 64th.

Everybody has their own, "good enough."

Cool eh?

Frosty The Lucky.

[ThomasPowers]

I once worked with a woodworker who had been making custom interiors for private jets. He like to split the pencil line when cutting wood...Machinists usually are good about taking tolerances into account.

[JHCC]

My mentor in cabinetmaking used to say, "Wherever you cut relative to the line, do it the same each time!" My boss in the violin repair shop was a dead-on, right-on-the-line, only-mark-with-a-knife guy.

On the other hand, my last project in the forge relied on one measurement: "about half again as long as my anvil".

Different rules for different work.

[ThomasPowers]

Measure with a micrometer, mark with chalk and cut with a torch!

[customcutter]

While I was at the FABA meeting Saturday the instructor said that his tape measured to 1/16th of an inch, but it wasn't necessary.  I proudly proclaimed that my surface grinder could cut to .0001".  He said that he had read a quote by another blacksmith that said measurements should be in inches, half inches, half half inches, and half half half inches anything beyond that was senseless.  

[ThomasPowers]

It does get to the point where temperature swings will cause the material  to  exceed the tolerances of the measuring system

[Frosty]

2 hours ago, ThomasPowers said:

It does get to the point where temperature swings will cause the material  to  exceed the tolerances of the measuring system

Tell me about it. Dad got pissed if someone stood too close when he was working on some projects where tolerances were space craft level, half a millionth of an inch was common. A person's body heat was enough to make him have to recalibrate, he compensated for his body heat but someone else off center screwed everything up. He didn't just want to be left alone but another heat source within about 5'-6' was enough to make his job sometimes impossible. There were full days he'd set up and check, set up and check for 8+hrs to make ONE cut. The company was thrilled, he could pull it off using a 1930s Navy surplus lathe. 

It was crazy and a major reason I didn't want to be a machinist anymore. Blacksmithing visceral control systems and mark One eyeball measuring. It was how I decompressed and I wasn't allowed near the close work.

Frosty The Lucky.

[Theintegrator]

Way off original topic but I gotta add that as a woodworker for 40 yrs working with steel surprises the heck outta me every single time I face. That's why I like it of course but every day is a new and usually an 'oh shoot' moment. Like, who knew u could actually apply enough heat trying to weld hss to 1/4 in mild steel that it would bend the 1/4 in mild steel?  I mean, wow. Wood doesn't do that. 

[Frosty]

Really? When I do things with wood it bends pretty often. Think it's a trick worth money? 

Frosty The Lucky.

[Tommie Hockett]

Shoot yeah if you can do it consistently hahaha.

[customcutter]

Steam and pressure.  It's how they build those beautiful cedar canoes.

Sorry we're way off topic again

[Theintegrator]

Back on topic; one last thing

 

the shelf for the forge? I know firebrick is not the best (interesting that its evidently a heat sink), but is an alumina shelf the right material?

[Mikey98118]

Circumstances alters cases.

I have seen sales jerks push stuff off on the unsuspecting, which they called "high alumina," which couldn't qualify for the term in any reasonable universe; so, start with, "do you trust the seller?" I buy from Seattle Pottery Supply, and have never had a problem.

High alumina kiln shelves are tough and reasonably heat reflective; they also stop flux. But, you can do well enough for less trouble with Kast-O-lite 30, and probably for less money in a small enough forge. The main reason I like the shelves in tunnel forges, is that they can be conveniently trapped in the forge shell. But, what if you're including a forge door on one end? That kind of ruins your ability to trap easily the shelve.

Finally, the newest insulating firebrick can now be given a heavy coating of zirconium silicate, and up your whole game. You gots to read some before you jumps...