FW: [TheForge] Mineral Wool ,ITC 100 efficacy ?

[Jerry Smith]

Mikey,

I am sorry to sat, but it's too nice out to be reading
news groups and email. 

Jerry

--- Kathy <keporter at comcast.net> wrote:

> 
> 
> -----Original Message-----
> From: Kathy [mailto:keporter at comcast.net] 
> Sent: Monday, May 28, 2007 10:34 AM
> To: 'artgawk at thegrid.net'
> Subject: RE: [TheForge] Mineral Wool ,ITC 100
> efficacy ?
> 
> Pete,
> Well, we've danced around the subject long enough,
> and now it's time to look the
> nasty in the eye. I think we both had an ugly
> suspicion that the coating simply
> amounted to "too little, to late." Convection, from
> all that I have read, is the
> big factor in heat transfer within kilns, and they
> are all designed to promote
> it (for the sake of even heat transfer to whatever
> pottery is being fired).
> Unfortunately, convection also moves the heated air
> over the kiln's walls,
> floor, and ceiling with equal thoroughness. Because
> a kiln has far greater
> exterior surface dimensions through which to leak
> heat via conduction, the IR
> coating may amount to "bailing water out of a holed
> boat." In other words, it is
> working, but the problem is so great that the help
> it provides becomes less than
> significant.
> 
> Now, we come to the ugly part; dealing with the
> beast. Pottery kilns sold to
> artists and hobbyists have only one course of
> bricks, which are positioned so as
> to cover the maximum space with the least bricks,
> keeping the cost of
> construction low for the manufacturer; they also do
> the worst possible job of
> insulating this way, which is just "tough luck" for
> the user. Personally, I
> can't complain about these facts, since the
> resulting electric bills and poor
> performance causes most of their purchasers to sell
> or give them away. A
> complete stranger gave me two of them in return for
> just hauling them off.
> 
> Naturally, the only effective solution to this
> problem is secondary insulation.
> However, the electrical controls must still remain
> on the kiln's exterior, which
> means that they will have to be moved further out,
> so as to remain outside of
> the second insulation layer...at this point, the few
> people who have thought
> things out this far become discouraged and dump the
> overpriced (now hated) kiln
> into the waiting hands of some despicable
> unscrupulous dog (arf, arf) Why they
> do so is a mystery, as the output for a second layer
> of insulating bricks is
> only about 1/20th the price of the kiln was the
> first place. Not only are more
> insulating bricks the obvious solution, but they are
> also the most expensive.
> 
> Fortunately for such vultures as myself, the poor
> innocents who are stuck with
> this dilemma seldom seek answers from a professional
> hot glass worker, or they
> would find out how easily water glass (sodium
> silicate) can be combined with
> perlite (from the nursery section of Builder's
> Emporium) to form a moldable
> ultra light insulating secondary refractory. Nor, do
> they spend time on groups
> like Castinghobby, where they can hear about calcium
> board, which they might
> purchase for very reasonable prices through some
> construction supply dealers (it
> is used as low cost light weight fire insulation in
> commercial buildings). No,
> poor souls, they never find out how easily the
> problem can be solved, but you
> just did >:-)))
> 
> Mikey 
> "I can live with the tail, but the fleas are
> murder!"
> 
> -----Original Message-----
> From: Peter Fels And Phoebe Palmer
> [mailto:artgawk at thegrid.net] 
> Sent: Monday, May 28, 2007 12:32 AM
> To: Kathy
> Subject: Re: [TheForge] Mineral Wool ,ITC 100
> efficacy ?
> 
> 
> 
> Kathy wrote:
> > Pete,
> > You make good points in your reply. The IR coating
> does make a significant
> > difference in interior temperatures. I have
> satisfied myself on this point
> many
> > times. Therefore, you should see a significant
> difference in s-o-m-t-h-i-in-g.
> > The question is in just what?
> Hi Mikey;
> I thought i would too.
> Because Phoebe hasn't been firing uniform loads, (
> tiles one 
> time, standing sculpture the next, glaze VS bisque
> etc) ..the 
> results are a bit muddied....
> But  still, we had to run a firing till 4:30 AM the
> other 
> morning...that was a first. Yawn
> > 
> > You wrote:
> > "Internal distance dissipation losses should be a
> minor consideration in a
> > sealed refractory vessel, and a constant in this
> instance."
> > 
> > Agreed; the point I was attempting to make with
> statements about square of the
> > distance losses and the very small size of the
> target area (the cone) was that
> > IR reflection (actually IR generation) would make
> no difference in droop time
> by
> > any direct impact on the cone; the gains would
> have to be from reduction in
> > conduction losses through the brick. All an IR
> reflector coating does is
> > generate IR from convection gain and IR gain on
> the hot face side of the brick
> > or other insulation. The generated light returns
> energy into the internal
> > system, slowing conduction losses through the
> brick. Probably, its most
> > significant contribution to heating within a gas
> forge is that it provides a
> > superheated surface area, which acts as a "giant
> match" surrounding the
> gaseous
> > contents, and completely upgrading the nature of
> combustion within a forge or
> > furnace. This factor has been thoroughly
> documented in industry, and is
> probably
> > beyond dispute. Coatings in an electrical
> appliance cannot gain from this
> > benefit and will only gain from reduced conduction
> losses. However, I would
> have
> > thought they would be significant; especially in
> something as large as a kiln.
> > 
> > You also wrote:
> > "I thought that an increase in IR reflectivity
> would decrease the 
> > amount of heat the walls leaked, leading to
> shorter firing times.
> > The only repeatable indicator we have for internal
> kiln 
> > temperature are the cones."
> > 
> > You should be getting a reduction in energy loss
> through the brick, and the
> > amount of the reduction should increase with
> temperature rise, but I don't
> > believe the cones, which are only designed to
> indicate absorbed energy of the
> > kiln contents can be used to measure the
> effectiveness of the coating.
> 
> If the coating works, then it should make the most
> difference at 
> the end of the firing where the losses nearly
> balance the heat 
> input, drawing out the firing time to raise it the
> last couple of 
> hundred degrees. I'd expected it to be pretty
> dramatic. Wrong.
> 
> > Electrical use, and time needed to due the firings
> are going to be your only
> > indications of the coating's effectiveness. So, we
> agree that the coating
> should
> > have decreased your firing times, supposing that
> you aren't using automatic
> > controls. If you are using automatic controls, it
> is only going to decrease
> your
> 
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