[TheForge] chip shapes and materials

[Jerry Frost]

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

Meadow Lakes, AK.

http://www.artmetalradio.com/

From: "Demon Buddha" <osan at netlabs.net>


>>
>> That would be my misuse of terminology. How about this, High heat 
>> resistance and high conductivity? It's what I meant.
>
> By "high heat resistance", do you mean high MP?  if so, then you are right 
> on.
>

I don't know what MP represents so maybe maybe not.

>> Agreed, almost as much a PITA as slip forming a lattice.
>
> I must disagree with you on this point.  The casting isn't difficult, just 
> time consuming... mainly because you must wait for the moisture to be 
> drawn from the slip.
>

Time consuming, unless it involves sleeping, lazing in the sun, etc., 
constitutes PITA especially if there's something faster and easier 
available.

> > So how about we
>> compromise and slip form hollow spheres?
>
> I have a better idea than that.  how about a polystyrene core that sits 
> inside a hollow cavity into which you case refractory cement.  When it 
> sets, it is at a far higher strength than clay so that it is less likely 
> to fail during burnout and firing.  Refractory cement also tends to be 
> more conductive than the high temperature clays, a good thing.
>

Kinda sounds like Bruce's idea using polystyrene instead of wood. More 
workable for sure but we're still working with a two part mold and set time 
for the slip. Still probably a lot easier than swirling.

> > That'd be really simple with a two part gang mold.
>
> It'll work but I think it is a lot of hassle.
>

Do you seriously think this would be more hassle than slip forming latice 
cube halves and "glueing" them together? If so I know a LOT less about slip 
casting than I thought.

>
> But if this is the case, then there is no point in using the chips. This 
> is why coal and charcoal are superior: they hold heat in the blast area 
> but radiate comparatively litte outward into the atmosphere, if the fire 
> is well structured.
>

No, charcoal and breeze burn radiating heat in the blast, they insulate 
outside the blast in a properly structured fire. A chip forge is heated by 
gas/air burning in the chip bed so the chips are only the heat reservoir. 
So, while it is important for the chips to have a high specific heat it's 
more important they yield and absorb it easily. On balance of course. If the 
chips were good insulators they would absorb heat from the fire slowly and 
yield it back slowly.

For a perfect example, I'm sure you've seen the yellow hot shuttle tile held 
in bare fingers by the corners. Yes? Shuttle tiles would suck giantly as 
forge chips. they also have low specific heat but the near zero conductivity 
is what I'm talking about.

>
>
> They are pretty tough, but don't forget that metal is going in and out and 
> this will be hard on the refractory.  I cannot say that I'm thrilled about 
> the idea.  I came up with this many years ago and wondered how well it 
> would work.  Apparently it is used commercially, if I recall correctly 
> from an earlier post.  If so, then clearly my intuition is flawed.
>

Very true but you don't have to jam steel in and out of the fire. I don't, 
it screws up the fire, damages the fine work and isn't good for anything. I 
don't know if it'll work either but think it's worth a try.

Frosty