James-

Parishville was a forest-industries town, and my smithy appears to have
been using charcoal, at least when coal was not available, to the end
(1904) simply because wood was so plentiful. I have been assuming that
the bloomery used charcoal for the same reason, but I will know when I
get out there and see whether there is coal slag. Sources of supply
appear to have been primarily local for everything from fuel to bricks
because of Parishville's remoteness. The bloomery, from the local
accounts, used both a water wheel for the hammer(s) and a venturi bubble
collector (similar to the one in Diderot's Encyclopedia) for the draft.
The ore is magnetite.

What is a run-out furnace?

Marty Pickands

>>> [log in to unmask] 04/25/06 4:12 PM >>>
Some basic terms.

If you are converting ore to metallic iron you are smelting. This is  
either done in a bloomery (which is a batch process and results in  
low carbon iron, sometimes called wrought iron) or a blast furnace  
(which is a continuous process and produces high carbon iron,  
sometimes called cast or pig iron). At least in terms of historic  
technology. Later you get open hearth, etc.

If you are removing either carbon or silicon from iron you are fining 

or refining it. Before 1783 this is done in a finery forge. It is  
possible that you might find a potting and stamping mill earlier than 

that, but the general consensus (which could be wrong) is that  
potting and stamping really never caught on in North America. After  
1783, but usually not until well into the 19C, this would be done in  
a puddling furnace. You can also have something called a run out  
furnace.

Assuming that you 19C smithy used coal and not charcoal you might be  
collecting clinker (coal residue), not iron slag.

Generally the following is true. A bloomery will have ore, charcoal,  
and low carbon iron. You will also find fayalitic slag, hammer scale, 

and mossers or skulls (what is left in the hearth at the end of the  
day). A finery will not have ore, but will have pig iron, as well as  
hammer scale, fayalitic slag, and mossers/skulls.

According to a number of sources, most good smiths could bloom. As  
what they produced was low carbon to begin with they would not have  
needed to fine it. They would have to consolidate the bloom and would 

want to fagot or pile weld it to end up with a piece that was  
relatively free of slag and homogenous.

In the Adirondacks in the mid to late 19C the American bloomery  
process is used. This includes hot blast and results in a much lower  
iron content slag.

James Brothers

On Apr 25, 2006, at 11:44, Marty Pickands wrote:

> I collected a fair amount of slag from a 19th c. blacksmith shop in
> Parishville, St. Lawrence County, NY, in hopes that I could compare
it
> with slag from the small bloomery once located at the other end of  
> town.
> Local tradition says that the other smith in Parishville was
refining
> this ore in his own shop after the bloomery shut down, and it would
be
> useful to know whether my smith was doing the same. Does anyone  
> have any
> suggestions for kinds of tests I might use?
>
> Marty Pickands
> NYS Museum
>
>>>> [log in to unmask] 04/24/06 6:20 PM >>>
> Best place to start is Robert Gordon's American Iron (Johns Hopkins
> 1996). It has a good chronology of how things were made and the
> results. If you don't own a copy, you should. Bob has also produced
a
>
> number of papers and a couple of other books on various aspects of
> the iron industry (including slag analysis). If you want something a
> bit smaller, and I think quite good (I wrote it), look at "Blast
> Furnace, Forge, and Foundry" (pp 335-353) in Uplands Archaeology in
> the East: Symposia VII & IX (available from the Archeological
Society
>
> of Virginia). I also have a 70 page bibliography I'd be happy to
send
>
> you (as I wrote my MA on the Virginia colonial industry it is a bit
> heavy on that, but covers the US/UK up to 1900). If you want to do
> research your problem will be getting references. Very few libraries
> have anything, expect to use inter library loan a lot.
>
> There is not a great deal on slag. Unfortunately many archaeologists
> don't even collect it. And if they do they seldom ever either
> describe it or have it analyzed. It is commonly mischaracterized as
> "clinker".
>
> Almost all blast furnace slag is glassy. But it can take on
different
>
> textures depending on how it was cooled (the Us Govt produced a book
> on how to do this in the 40s). This is because it is, for the most
> part, a silica-lime glass. Lime is used as a fluxing agent.
Generally
>
> it is green or gray green, but other colors are possible including
> blue, white and red (it all depends on what is in the ore).
> Regardless of whether or not it is hot or cold blast, charcoal or
> coke, it will still be glass and glassy. If it is tapped out onto a
> surface containing a lot of moisture it will be full of airholes. If
> it is cooled quickly it will tend to look stoney. But regardless it
> is still chemically glass. Batso, after it stopped making iron, used
> the slag pile to make bottles.
>
> Finery and bloomery slag are not glass, they are fayalitic
(Fe2SiO4).
>
> And may contain up to 70% iron. The bloomery process is "self
> fluxing" and it is the iron that makes the slag liquid. Bloomery
slag
>
> will often contain chunks of charcoal and unreacted ore. Finery slag
> may contain chunks of charcoal. Both are usually dark brown to
almost
>
> black and have a ropy texture.
>
> Foundry slag is also different, but I really haven't seen much. As I
> remember it may have an almost metallic look to it.
>
>
> On Apr 23, 2006, at 22:49, Ben Ruset wrote:
>
>> Hi All:
>>
>> I'm in the process of writing an article on the bog iron industry
>> in the New Jersey Pine Barrens for my website, and had a few
>> generic questions related to blast furnaces, forges, and slag. If
>> someone can point me to some good source material, or even answer
>> my questions, I'd be much indebted.
>>
>> Firstly, there is definitely a difference in the type of slag that
>> is produced by a blast furnace and a forge. Within the scope of
>> furnace slag, it appears that the slag is different depending on
>> whether the furnace used the cold blast method, or the hot blast
>> method. From my understanding, cold blast furnaces tended to
>> produce very rocky, metallic slag that in some ways resembled
>> pyrite in texture and form. Hot blast furnaces produced slag that
>> is almost glass-like. Is my assumption correct?
>>
>> Forge slag seems to look just like you would expect a pool of
>> cooled iron to look like. It is smooth in texture, without a lot of
>
>> visible impurities (ie: no unburnt charcoal, etc.) Are there other
>> ways of telling if forge slag is in fact forge slag?
>>
>> I have seen varieties of cold blast slag and forge slag, and what I
>
>> assume to be hot blast slag, although it was at a site that I was
>> unaware used hot blast technology.
>>
>> Secondly, when it comes to forges, it seems that many had both a
>> stamping mill as well as a tilt hammer. The thing that I am unclear
>
>> on is what the main difference in the finished product of both
>> were. I have scoured "Early Forges and Furnaces in New Jersey" but
>> it is pretty unclear to me what the main differences are. If
>> anybody can shed some light on the subject, I'd really appreciate
> it.
>>
>> Thanks!
>> Ben Ruset