Saturday, December 26, 2015

Pressure in a Bloomery Furnace?

 (I had made a detailed response to a question on the Bladesmith Forum - 'Bloomers and Button's'. This is edited from that conversation...)

What I haven't seen though is any talk about the internal pressure of the furnace and what effect it has on a bloom. I was thinking of modifying one of the Rockbridge furnaces to increase the internal pressure as a way of increasing the temperature.

Has anyone tried doing this? If so, was it helpful? Hurtful? Aside from a different way to regulate temperature, I'm speculating that the rate of reactions inside the furnace would increase at a higher pressure, so I wanted to try it to get a better yield.

(link to complete thread)

My team here has made some input pressure readings. Honestly using fairly cobbled together instruments. This primarily to counter criticisms (largely from theoretical academic commentators) that all the current work is not 'scientifically rigorous' enough.
(But like Lee Sauder says : 'If you don't get any iron - whatever you have done *has* to be wrong'.)

The first thing we tried (cheap and only a relative measure) was a simple U tube with water in it attached to the tuyere side. This gave us some rough ideas - at least between individual smelts.
Eventually I got a small guage (off E-bay) that measured 0 - 30 psi range. (The trouble I had was finding something in the right range, at a price I could manage.)
Some of the individual smelts in our series here have the input pressures measured. You would have to check through the individual 'smelt data' records one by one - there is no centralized table with all the variables charted from all the experiments. (Neil and I am working on that however - with plus 60 smelts, and so many measurement points, its pretty ugly.)

Overall, the average we recorded for input pressure at the tuyere was 3 - 5 PSI.*

We also were using a rough guage for input volume. This consisted (budget again) of a wind surfer's speed guage placed across the input pipe. The volumes were calculated mathmaticaly from the flow speed. Again not the ideal, and it turned out fatigue in the vanes at the high speeds measured really effected instrument performance with time.


I have been using a different method than Lee uses for controlling the input air from the electric blower. (I've managed to purchase one of the same high end blowers he uses by the way). You can see the sliding plate gate (from a dust collection system) located just at the exit from the blower. So I'm limiting the amount of air into the entire downstream system. (Lee uses a moveable plate just in front of the tuyere set up, venting off excess air.) Both of us have some rough calibrations on these valves that let us have some rough approximation of the air we are providing to the overall system. Mine is marked (very rough approximations!) of 100's of litres / minute (based on earlier measurements). Lee's (was) marked in fractions of total possible (1/4 - 1/2 ...)

My smelting partner, Neil Peterson, is driving an experimental series investigating Viking Age glass bead making furnaces. (Even *less* archaeology than for iron smelting furnaces!). He has deeper pockets than I certainly do (!) and has recently invested in a multi input data recorder system. Along with high temperature probes, he has purchased some modules that will record pressure, and a better quality vane type air speed (so volume) instrument. We still have to assemble the fittings and run some tests, but we have good hopes for better (more consistent) measurements into the future.

You may have gathered from all that - my thrust here has been to researching possible historic *process* - with less concentration on *product*.
I have to agree with what Mark Green has said : That historic air delivery systems may not result in the most efficient utilization of ore = not the best quality blooms. You most certainly can *make* iron in lower air systems (and this most certainly was the method for much of human made iron production). What many researchers miss is the second stage - of bloom to bar. What you may gain in simplicity from ore to bloom is competely lost by the extra labour / materials converting a lacy bloom into a working bar.
Lee has much better experience / notes / observations about this aspect.


Lee and Skip experimented and documented and then introduced to all the concept of high volume air = better ore to bloom conversion, both in terms of size and density. (Historic note, look at the impact of water powered systems circa 800 - 1100 AD in Europe  - pretty much the same thing!)

Although some experimenters have produced measurements of input air pressures, I am uncertain that anyone has attempted to measure pressures inside the actual furnace itself.

As Mark as mentioned, delivery air needs to be considered in terms of not only *volume* but also in terms of *pressure*.
This is why people attempting to use rotory blacksmith's forge blowers as air sources often have less than the best results. Those equipments produce a large volume - but at virtually no pressure. The air simply does not penetrate through the tuyere diameter into the charcoal mass. Increasing the diameter of the tuyere might assist this. Using multiple tuyeres would certainly help (and both methods are seen in historic systems.)

But in actual fact, none of us need to really worry so much about absolute pressure measurements, or even with measuring air volume. The best 'working' measurement is via charcoal consumption. Rate of charcoal consumption is also the effect of internal temperature and size of the effective heat zone. Bigger and hotter = faster charcoal burning.

Most of us are working on some variation of the 'Sauder System', what historically I would call the 'short shaft' furnace. Most typically our working furnaces have an internal diameter of closer to 10 - 12 inches.
This is quite important when discussing measurements and working methods.
As you have seen, there is a dance between ore / charcoal / furnace  / air. My own experience is that there is no *absolute* 'perfect' furnace. Any basic design will have to be modified based on changes to those four primary elements. Hematite will not produce the same results, even in identical furnaces and method, as the bog iron ore analog I typically use here.

I'm (educated?) guessing that any attempt to modify the internal gas pressure in what is a very rough and simple furnace will prove far more effort than effective in result.
Past experience has proved the simplest way to effect the reaction ability of a furnace is just to increase the total stack height. (Nice example there, Mark gave 40 inches as his ideal stack height - I usually build for closer to 24 - 30 inches. My standard furnace diameter is larger, rarely below 10 inches, to his reported 8 inch minimum. I know we are working with quite different ore types, and maybe charcoal as well.)
There are just too many other variables for a 'one size fits all' design. (So many things that can, and often do, go wrong!)

Monday, December 14, 2015

Carbon Loading

After Paris, there is a lot of talk about Carbon Production, leading perhaps to a Carbon Tax here in Canada.

I had looked at this a couple of years back:
Carbon and the Forge
At that point I was primarily interested in the amount of C02 loading from the various fuel options in a blacksmithing operation. I used my own consumptions and choices at that time for the comparisons.

I (attempted) to run the numbers for a 'typical' year of operations, using the totals from my own 2015 records

Gasoline = approximately 3000 litres
(this worked back from actual $$ spent, using $1 CDN per litre as a very rough average cost)

Coal - approximately 1000 lbs
(this very rough, as I purchase in 1500 lb lots, as needed only)

Propane - close estimate 800 lbs
(this fairly accurate, based on the number of 40 lb tank fills made)

Charcoal - approximately 300 lbs
(this a bit of a WAG, based on three iron smelts per year, each at 100 lbs each)

Ok - Now the fun starts.
There may be some simple chart out there converting fuel type and amount into 'best possible' CO2. I certainly could not find one. In the end I had (again) to make several conversions between pounds / litres / US gallons * ....
What I came up with:

Gasoline - CO2 lbs per US gallon = 19.6 : use total = 15,523 lbs CO2

Coal (Bituminous) - CO2 lbs per ton = 4931 : use total = 2465 lbs CO2

Propane - CO2 lbs per US gallon = 12.7 : use total = 1070 lbs CO2

Charcoal - CO2 lbs per lb (dry oak, molecule based) = 2.9 : use total = 880 lbs CO2

There is a small amount of Kerosene and split dry firewood used around the shop, but here considered too small to add.

TOTAL CARBON DIOXIDE LOADING = 19,938 lbs / about 10 tons ( just over 9 metric tons)

I note that this year I did not make as many long range working trips (driving). Even still, gasoline use is by far the majority (roughly 3/4). As a rural resident, and involved in a small business, I'm not sure how I could easily reduce there.**

As a comparison, I did take a look at a 'Household Footprint' calculator (which is almost so vague to of little use). Outside of the workshop, the major 'carbon' expense here would be related to heating. At Wareham, this is primarily electric - which plugging in the total $$ last year suggests a CO2 load of 12 tons (At this location is mainly via Bruce Nuclear. Wareham is at the north end of the Shelburne wind turbine complex, but honestly I have no idea how much that actually contributes to the local power grid.
I also burn about a full bush cord of locally cut firewood every year for additional heating. ( An estimate on that is 6,670 lbs CO2 produced)

This suggests a total of 15 + tons CO2 from the Household side.
(There would be some additional amount from the food purchase made over the year. Economics here dictate there is very little 'new' purchasing - Used items and 'from the dump'  are the norm.)

So - what this all comes to is that the actual forge fuels contribute by far the smallest  portion to my own personal 'carbon load'

* I had originally stumbled on a USA Environmental Protection Agency set of tables, but through doing one thing after another, lost the specific link. These totals are taken from my working notes (sorry to the 'evidence' hounds)

** I own two (virtually 'classic') vehicles :
2003 Chev Astro, cargo, with a 4.3 L six cylinder
1997 Honda Odyssey, basic, with a 2.1 L four cylinder
This year 3/4 of the distance has been using the smaller engine Odyssey - and it is virtually all highway driving.
Question :  Admittedly an older version is most likely to be less efficient, and thus generating more CO2 per litre / kilometer. But against that is the 'production' energy / carbon cost of a new vehicle. Which is, in the final accounting, the lower carbon impact?

Thursday, December 10, 2015

Blacksmiths Captured...

The Blacksmiths

A personal photography project about blacksmiths and their craft.

My name is Dan Bannister, and I’m a commercial photographer based in Toronto, Canada. My day to day photography work is mostly advertising and fashion for retail brands but I like to add variety to my photography and exercise my creative muscles by pursuing personal projects alongside my commercial work as much as I can.
... a man named Lloyd Johnston, who has this incredible resume as a blacksmith, including being the person responsible for the historically accurate restoration of the iron gates on Canada’s Parliament Buildings.
This eventually led me to meeting other blacksmiths and photographing a number of them as well as making a mini documentary of Lloyd working in his shop ...
Lloyd Johnston Image by Dan Bannister

Link to  The Blacksmiths

Link to Dan Bannister

Dan started this series a number of years back. My memory is that he had taken some of his first images at CanIRON 8, back in 2011. I vaguely remember having someone taking images of a number of us, especially his focus on 'object in the hand' - which you see expanded on in the published series.
Reguardless of that, I highly recommend that you take a look at 'The Blacksmiths'. These are simply wonderful character captures - many of people I know from here in Ontario.

Great work Dan!

Wednesday, December 02, 2015

'Forged in Fire' - 2


Yesterday I ground the rough forged blade to what is more or less its intended shape

Rough Forging
Ground to Shape
Compared to the rough forging, you can see the first modification is cleaning up the blade outline. This was not changed very much, really just smoothing out the lines from the forging.
The main modifications here were changes to the shape of the handle. I decided to put a slight inside curve to the top side. I have also slightly straightened the lower side, and steepened the front end to increase the 'catch' to the index finger.
Likely I will put a short unsharpened area (riccasso) just at the base of the blade side in the final polishing.

Additional time spent = + 5 minutes
(total time to this point = 70 minutes)

See the earlier full review of 'Forged in Fire' on this earlier post

PS - On the Photograph
The flow of ice that frames the blade was a completely natural formation on my deck!

Tuesday, December 01, 2015

Quad State 2015 - Gallery

Every year, I attend the regional blacksmith's conference put on by the Southern Ohio Forge and Anvil - QUAD STATE.

One of the features of the gathering is a gallery of participant's work. This is an open display, but awards are given in specific categories. Every year there is a specific theme for a special award. Over the years the quality of the objects submitted has increased amazingly. (More and more pieces that are 'I wish *I* had made that'!)

Although this is a bit delayed, here are the pieces in 2015 that really caught my eye...

Table by Micheal Bendele 
forged copper with wood plank top

I have always loved Micheal's work - and have been a bit in awe of the scale and the lines of it.
This piece was fairly large, about five feet wide by about eight feet long, standing at 'dining table' height. The legs were all different, forged from bundles of about 3/4 inch diameter solid copper. The overall theme was 'octopus'.

Copper Vessels by Franco Ruffini 
raised copper sheet, gold leaf, sterling silver

In contrast with Micheal's table, Franco's work was quite small in scale. Most of the pieces were roughly fist sized. The detailing here was nothing short of amazing. The gold leaf applied to the interior surfaces of many of them caught the light in a spectacular fashion. Some might quibble that strictly speaking this is not hot forging work, but the quality of the series was exceptional.
(I was able to have a long conversation with Franco about this work, and came away quite impressed with his attitude to art metalwork in general, and this series specifically.)

'Devil in the Details'
forged steel, copper details

This piece, by an artist who's name I did not record, simply blew me away. The overall size here was about 30 inches long. As the title suggests, the fine work and degree of forged sculpting in the individual elements was incredible. (These images hardly do the piece justice, I wish I had taken a close in view.)
In the end, this was the piece I voted for as 'best of show'. 


February 15 - May 15, 2012 : Supported by a Crafts Projects - Creation and Development Grant

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