Forges 101

[Mikey98118]

This ain't rocket science

No secret fumed silica to water ratio  has been given in these pages. I have stated repeatedly that people can mix the fumed silica into the water until it gets too thick for the spritzer nozzle to handle, and then add more water. There is no perfect ultimate ratio; that is a myth. Handling rigidizer is easy; don't try to make it into something complicated already!

[Mikey98118]

On the other hand, the thinner the rigidizer is mixed the faster and deeper it penetrates into the ceramic blanket, so what to do if it is too thin? Fire the blanket to set the first coating in place, and then rigidize all over again. Want to have a better idea of how the process is proceeding? Then mix food coloring into the rigidizer as a visible clue; it burns out during firing.

Finally, it seems that most guys have way too much concern over getting the fumed silica to water ratio "correct." Perhaps this worry comes from a mistaken idea of how rigidizer works and what it is for. The fumed silica becomes colloidal particles when suspended in water The water flows over the ceramic fibers allowing the particles to accumulate at the cross-sections everywhere that the fibers intersect; those intersections are welded together during firing; this is what strengthens the blanket. The residue of silica that remains on the lengths of fibers is so thin--no matterr how much rigidizer you use--as to contribute nothing to the strength of the blanket.  

By the time your are rigidizing your forge's insulating blanket you should have a working burner with which to fire the rigidizer. You can rigidize and fire the inside of the forge all at once, or use the burner as a hand torch and rigidize and fire the blanket one area at a time.

[Mikey98118]

2 hours ago, Mikey98118 said:

Flame impingement issues

It is important to build a forge with the flame angled away from heating stocks (round forges) or with the ceiling far enough from the floor (square forges) to keep the flame from impinging on heating stock, I can answer your question about flame lengths; since different burners make different flame lengths and since flame lengths also vary by how far the burner is turned up, there can be no pat answer; it is a judgement call on the builder's part.

Since most people find little reason to turn a burner on full blast, the flame for a box forge can be measured for length at a maximum of 20 PSI gas pressure and that can be used for a good height measurement in box forges. You want the length to be at least two-inches beyond secondary flames. No practical forge can avoid tertiary flames, so construct and tune your forge's burner well enough to avoid making them.

However, flame length is only important if your burners are top mounted and facing directly toward the floor. Some guys mount the burners on sidewalls facing horizontally to get around early flame impingement altogether; this saves the heating stock and also lowers thermal wear and tear of furnace walls, which is the primary reason that burners are aimed toward the floor in box forges.

 

 

 

[Mikey98118]

K26 bricks

K26 Firebricks Insulate as well as ceramic fiber at 2000 F and up; they are inexpensive and lightweight. K26 brick, while more delicate than hard firebricks, will stand up to thermal cycling in a forge; they are use-rated for constant duty at 2600 F, so they only need a thin coat of castable refractory for sealant, although a heat reflective coating will improve their performance as well as with any other insulative choice.

Although the brick consists of hard refractory clay, live steam is used during construction to provide air holes, While carbide tipped holesaws are needed to drill burner ports in this brick, the process is still bound to be far less work than drilling burner ports in solid firebrick.

The point of this discussion at this time is that this new product has come along just in time to work out very well with advanced burner positioning in box forges (see above).

Being new on the market, this brick is hard to find at present. But it is available on eBay; because of its low weight, shipping charges are very reasonable.

 

[Frosty]

K26 is also available in many sizes from large blocks to thin sheet. Standard ( 2.25" x 4.5" x  9") brick size is just the most common size used not the only thing they offer for sale. As more demand develops more sizes will become available without having to special order. 

In Anchorage Ak. they're just a bit more than 1/2 the price of common insulating light fire brick. I believe because there is less breakage in shipping. 

Frosty The Lucky. 

[Mikey98118]

More on burner positions

During a discussion about scale formation, a member here states "I try to stay out of the direct flame if I can but I usually have several pieces in at once so it’s not always possible.  I’ll just have to work with it."

And here we have still another reason for positioning burners high on a forge wall and aiming them horizontally toward the opposite wall in a box shaped forge, or upward in a tunnel  or "D" shaped forge; thus gaining the maximum distance for the flame's super-heated oxygen molecules to combine with escaping fuel molecules before the oxygen can impinge on work surfaces. 

[Clyde_Ulmer]

On 5/29/2018 at 4:16 PM, Mikey98118 said:

More on burner positions

And here we have still another reason for positioning burners high on a forge wall and aiming them horizontally toward the opposite wall in a box shaped forge, or upward in a tunnel  or "D" shaped forge; thus gaining the maximum distance for the flame's super-heated oxygen molecules to combine with escaping fuel molecules before the oxygen can impinge on work surfaces. 

I've been re-reading Forges 101 in preparation for my latest forge build. I have a decent propane tank tunnel forge -- 2" Kaowool; Satanite hardface; ITC-100 coating; Frosty T-burner at 2:00 o'clock, tangent to the inner face  -- but I wanted to pimp out a new one with everything I've gleaned from here. I've been planning to mount the burner at 4:30 - 5:00 o'clock not only for the reason Mikey stated, but because it seems to me that such positioning would negate problems with chimney effect and hot exhaust gases mucking with air intake. So, I'm heartened to read Mikey's statement here.

Moving laterally a bit, I was recently in a commercial restaurant supply store and ran across a display of woks that went up to 30" (!!!) diameter. The thought ghosted through my mind that two woks and a ribbon burner might an easy clam shell forge make 

Clyde

[Exo313]

On 2018-05-24 at 5:59 PM, Mikey98118 said:

...K26 firebricks... only need a thin coat of castable refractory for sealant, although a heat reflective coating will improve their performance as well as with any other insulative choice.

Thoughts on using refractory mortar for joints as opposed to castable? I'm also unsure what you mean by sealant unless you're talking between the bricks. I wouldn't think the faces need sealing?

[Mikey98118]

These bricks are full of steam holes; this is how a hard clay refractory can come even with ceramic fiber blanket at forge temperatures. Sealing their hot-face  surfaces to keep flame impingement at the surface, not in the brick, is only common sense. Morter is fine between the bicks--not on their faces.

7 hours ago, Clyde_Ulmer said:

The thought ghosted through my mind that two woks and a ribbon burner might an easy clam shell forge make 

If you centered it in the top shell it should work very well.

[Mikey98118]

I think that a very few K26 hard insulating bricks of various thicknesses, down to 1/2" with a finish coating would serve much better to finish small oval forges with than a second layer of ceramic fiber blanket, for about the same amount of money, and be much easier to work with to finish up with the desired forge.

[Frosty]

For the floor Mike?  I've lost track of where we are on this thread,  a 9 week old puppy can be pretty distracting. 

Frosty The Lucky.

[Mikey98118]

I would recommend them for wall, floor and ends; the only thing I would add on the floor surface is an extra thick coat of cast refractory over the brick, for protection against hot flux.

[Daguy]

So I have everything I need To begin my build (Thanks, Wayne, for the refractory) except for the rigidizer.

"But, Daguy", you ask, "WHY don't you have rigidizer?  You know it's a necessary component for safety.  You're a safe guy.  You usually prefer to do things right.  Why?"

And I reply thusly:  "I am a maintenance mechani in a food production facility.  We make non-dairy creamer.  (By the way,if you use non-dairy creamer for your coffe, switch to halfand half ormilk or something that isn't made with chemicals.  Keep reading and you'll discover one of the reasons.)  Two of the ingredients we use in different recipesis calledconditioner.  It helps to facilitate the product flow through the production and packaging machinery.  The brand names are Zeolex 23 and Zeofree 80, hereafter to be referred to as either 23 or 80.

 

23 is Sodium Aluminosilicate.  Some excerpts from the MSDS:   

Melting point / Freezing point > 3092 °F (> 1700 °C) 101,3 kPa

Water Solubility 68 - 79 mg/l (Na+, Al3+, SiO2) (20°C, pH ~9)

Inhalation Avoid inhalation of the product. Inhalation of dust may cause irritation of the respiratory system.

Water Solubility 68 - 79 mg/l (Na+, Al3+, SiO2) (20°C, pH ~9)

 

80 is Synthetic amorphous silica.  Excerpts from MSDS:

Melting Point / Melting Range > 3092 °F (> 1700 °C) 101,3 kPa

Water Solubility 0.0031 g/l Water 20ºC

Inhalation Avoid inhalation of the product. Inhalation of dust may cause irritation of the respiratory system.

Water Solubility 0.0031 g/l Water 20ºC

 

So are either of these silicates useable as rigidizer?  It is still clean, but since it has left containment can't be used for conditioning product, soI can get twice as much of either conditioner (Clean) as I can use in a lifetime by sweeping up the spillage from around the machine that blends it into the product before it is cleaned up and thrown into the pig feed totes. 

I mixed some of the 23 in water and it went in to solution, but settled mostly out after an hour or so.  the water was still translucent white, but there was a layer of solid product at the bottom of the container.  Think Corn starch.  Yes, it emmulates corn starch quite closely"

 

So my questions are:

Do you think it's usable as rigidizer?  would I negatively effect my ceramic blanket by an attempt to use it?  Or would the worst case scenario be that I'd need  follow it up with a real hydrophilic fumed silica if it failed to bond?  How would i judge the results of the attempt?

 

Any feedback/input from the gurus?

 

 

 

[Mikey98118]

7 hours ago, Daguy said:

Do you think it's usable as rigidizer?  would I negatively effect my ceramic blanket by an attempt to use it?  Or would the worst case scenario be that I'd need  follow it up with a real hydrophilic fumed silica if it failed to bond?  How would i judge the results of the attempt?

#80 will probably work okay; it should  only need to remain in solution long enough to be spritzed onto the blanket; fumed silica will remain in solution for months or even years; the advantage for newbies is certainty. You are a grown up; I think this is all the "go for it" you need.

But 23 is Sodium Aluminosilicate. The alumina content is superior to silicate; together they match the content of the ceramic fiber...BUT the salt content will lower its use temperature rating; how far will depend on how much salt content. In other words, it's a crapshoot.

[Daguy]

2 hours ago, Mikey98118 said:

#80 will probably work okay; it should  only need to remain in solution long enough to be spritzed onto the blanket; fumed silica will remain in solution for months or even years; the advantage for newbies is certainty. You are a grown up; I think this is all the "go for it" you need.

But 23 is Sodium Aluminosilicate. The alumina content is superior to silicate; together they match the content of the ceramic fiber...BUT the salt content will lower its use temperature rating; how far will depend on how much salt content. In other words, it's a crapshoot.

First, Thanks for the Reply, Mikey.  I was hoping someone on IFI would have a little more chemical expertise than I do.  Another Document:

 

                                                                                               ZEOLEX® DESCRIPTION:

Zeolex is a precipitated, synthetic sodium aluminosilicate and the first synthetic non-black filler. These silicates are semi-reinforcing fillers utilized in all types of elastomeric compounds to provide a broad range of elastomeric properties at a reasonable cost. They are available as powders with a range of surface areas from 75 to 115 m2 /gm. (BET).

                                                                                              TYPICAL PROPERTIES:

                                                                       Zeolex 23                                                         Zeolex 80

Average Particle Size (μm)                             6.0                                                                     6.0

pH                                                                      10.0                                                                    7.0

Surface Area (m2 /gm. BET)                           75                                                                     115

Specific Gravity                                               2.10                                                                     2.10

Sieve Residue, 325 Mesh, %                         0.10                                                                      0.10

Sodium Sulfate, %                                          2.50                                                                      2.50 

Moisture, 2 hrs./105°C                                  2.00                                                                      5.00

Oil Absorption, Linseed cc/100gr.               117                                                                       120

 

                                                                                                      APPLICATIONS:

Many compounds consider Zeolex products as the “go between” filler amid low structure silicas and hard clays. Zeolex products fill this gap nicely acting as semi-reinforcing filler with moderate abrasion resistance and good processing properties at a reasonable cost. Low surface area grades are well accepted in the production of extruded goods where surface smoothness is required such as: hoses, gaskets and flooring materials. The higher surface area grades have more reinforcing capability and have replaced precipitated silica in many rubber applications by improving cost, processing and hysteretic properties. Other typical applications include: footwear, belts, rollers, wire and cable, sponge, tires, molded parts and calendered goods. In addition, the high whiteness of Zeolex is ideal for non-black or color rubber articles. Typical loading range is from a low of 10 phr to high of 150 phr. ® Zeolex is a registered trade name of J.M. Huber, Engineered Materials Sector

 

So, would 2.5% Compromise the Insulating ability TOO much?

[Mikey98118]

That alters my view: Both products have salt content; and those contents are low, which is good, so you might as well choose the alumina containing mixture.

No; I don't think such a low salt content will ruin either product as a rigidizer; I well be looking to test it this summer. You have turned the table on me, and is pushing me into the peoples pool at the deep end

[Daguy]

Thanks for the input.  I'll be sure to report the results, though it may be a couple of weeks.  My Mother-in-Law just had hip replacement surgery and my wife and I are primary caretakers, so the forge build has to be put on a short pause.

 

 

[Mikey98118]

Frosty answered a question that is long overdue

A member wanted to change out his Kast--lite 30 forge floor for something even tougher for hot borax to mess up. It was pointed out that he could just use a thin layer of Green Cast, rather than replacing the floor. The following are his answers to the member's questions:

"htis No problem, they'll bond fine. Make sure the existing floor is clean and free of loose debris and wet it before applying the Green cast. They are very similar products the main difference is in % of alumina refractory to calcium binder (cement) and aggregate. The Kastolite contains evacuated silica beads as part of the aggregate and this makes it a little more susceptible to hot borax based flux.

In future when a refractory maker or furnace guy talks about "heat retention" here we talk about "heat sink" this is heat the refractory collects and holds onto. If you're running a high volume quick turn over furnace then a high heat retention furnace wall is a good thing. It may take more fuel to bring it up to temperature but it will stay hot longer when you open the doors to exchange hot for cold stock and close them up again, this makes the stock heat faster. Good for high production. This type furnace is usually left running 24/7 because of the fuel costs to heat it back up and the damage done by thermal cycling.

However what we do in a small smithing shop is slower paced, maybe a few hours a day two days a week. Maybe. For us we want a forge that heats up quickly and doesn't suffer for heating up and cooling off quickly. For what we do as little thermal mass as we can get away with is the better deal. However insulating refractories like Kaowool are fragile especially at forging temperatures not to mention shedding sharp ceramic fibers that are a breathing hazard. So, they need some armor, first stiffen it up in general with a rigidizer then apply a layer of something concrete hard and relatively immune to hot caustics like welding fluxes. 

I have some greencast 94 and the stuff is bulletproof for the worst I could do to it. I switched to Kastolite 30 for a couple reasons: It's less expensive, here anyway, more significantly it's a reasonably good isulator and most significantly it's concrete hard above easy welding temps and laughs at the welding flux I use. "Petersons blue." The Peterson's is off the shelf at the local welding supply for about $1/3 one of the "Forge Welding Fluxes" sold by blacksmith suppliers. The stuff's anhydrous borax, boric acid and something to turn it blue. Peterson's makes a flux that also includes iron oxide like some of the "real" forge welding fluxes but I can't understand why we brush so HARD to remove scale (iron oxide) just to include it in the flux. There's lots I don't know so take that as my opinion for what it's worth.

Anyway, I tested Kastolite 30 by putting a heaping Tbsp. on yellow hot Kastolite. Nothin, nada."

[Frosty]

On 6/25/2018 at 1:29 PM, Mikey98118 said:

Anyway, I tested Kastolite 30 by putting a heaping Tbsp. on yellow hot Kastolite. Nothin, nada."

This is from a post I made a while back regarding Kastolite 30 and forge welding flux. As it turns out I must have already kiln washed my forge before running the above test. Results other folk here have experienced with it and flux caused me to retest as their experience was much different. As it is Kastolite 30 is NOT proof against borax containing forge welding fluxes. Evidently %30 high alumina isn't a high enough % to be very resistant to hot flux, it dissolves Kastolite into a rather sticky paste. 

If it's available I'd love to hear how one of the Kastolite refractories with a higher % of alumina tests against fluxes. Now though you REALLY need to kiln wash it to protect it against hot flux. 

Frosty The Lucky.

[Mikey98118]

While, you included the update, so that's cool.

[Mikey98118]

To weld or not to weld; that is the question

Gee whiz Batman. How can we compete with those lucky guys with MIG welders? Life is so hard!!!

Not so much; unless those "lucky" guys also no what they are doing, they are very likely to weld up a frame that will warp badly in short order. Back before hydraulic machinery became ubiquitous in steel shops, one of a Burner's jobs was shaping difficult steel parts, like angle, with heat. When angles are left exposed to forge temperatures in the combustion chamber, while their outside legs are open to air cooling, a perfect receipt for warping is created. Welding can't stop the steel from warping, it can only make repairs harder to make.

Most warping takes place at around 400 degrees

Steel sheet that is welded rigidly in place can't move sufficiently during heating cycles, resulting in warpage. So, why don't tunnel forges made of steel tubing, or oval forges warp? Because, round surfaces have flex built into them; sheet and angles don't. So how do all those steel box forges keep from warping? They are designed to allow the steel parts to move were they need to.

So do we forget welding? No we carefully examine the construction those kind of forges, before reaching for a MIG gun!

[stevomiller]

Folks,

i found another IR heat reflective coating at a price 1/2 of the ITC .

Hybrid Burners sells it by the pint, it’s called HYB-UV IR reflective coating, claims to reflect up to 98% of the IR energy, said they had a refractory company formulate it for them so they could offer an effective cheaper alternative to ITC.

I bought a pint (it’s in transit)and will be using it in my first gasser which I’m building now from a Freon bottle, and 2” 2600* HP 8lb wool (I found a full box at work being thrown out). I have my Kastolite 30 and silica Rigidizer on hand, and a 3/4” burner I’d obtained before I learned from this thread that a quality 1/2” was sufficient. Last item I need to buy k26 bricks for movable doors, and either kiln shelves or materials to make the same for my floor. I’m getting antsy, it’s been over 20 years since I’ve done any smithing, and that was with good old bituminous and charcoal. Anyways, I will post pics when I’m done and anything I learn about the hybrid reflective coating.

[stevomiller]

Also, I looked up the SDS on Plistix 900, which I’ve read folks here state as having a high zirconium content.

Per the SDS, it is 94.1% alumina oxide, 1.7% silicon oxide, remainder unstated. Per this, it can’t be ZrO2, or at least any more than about 4%, but that would mean there’s also no binders, etc.e

[Mikey98118]

Since it's made by Plibrico, I look forward to seeing your results.

[stevomiller]

Hi Mike!

The Plibrico data sheet I included is for the Plistix 900 that others sell and recommend as the ITC100 alternative. As of yet I don’t know who makes the coating I bought from Hybrid, or what’s in it. I’m hoping the packaging gives me more info when it gets here Monday. Regardless i will post results once I use it, but it’s unfortunate I don’t have any reference or experience to compare it to.