Friday, July 05, 2019

'so damn WET'... Ore Analog consideration

A potential correction on reported yields?

For a good long while, the iron smelt experiments have used an artificial preparation we call 'DARC Dirt'.
The origins of this preparation go back to 2008, when we started on the 'Vinland' series. Here at Wareham, there is no available natural iron ore of any kind. (As I have mentioned in previous posts, Wareham sits at one end of the massive block of limestone that forms the Niagara Escarpment - a block roughly 400 + km long and about 100 m thick!). Although 'primary bog iron ore' can be found 100 km north of here (up on to the Canadian Shield), I have never found any more than the faintest traces of iron locally.
Primary Bog Iron Ore - from L'Anse aux Meadows (early 1970's excavations)
For the Vinland series, we wanted to have a dependable quantity of an iron 'ore', which would also at least approximate the chemistry of that known to have been used at L'Anse aux Meadows by the Norse. Our solution was to mix up an analog, using commercially available 'Spanish Red' Fe2O3 oxide powder.
One huge advantage is that use of the analog has given us a very consistent baseline within our many variations on furnace design and air systems testing. There have been slight variations of this standard mix, usually by adding various amounts of forge scale (so Fe3O4) to 'enrich' the basic mixture.

DD-1 analog as added in a working smelt (Vinland 1)
Details of this mix  *

Chemical analysis
Fe2O3    81  %
SiO2      5  %
CaO      2.3 %
MgO2     2  %
Al2O3    2.6 %
Loss on ignition 7 %

As DD#1
Red Oxide          82 %
Wheat Flour          8 %
Water (after drying) ≠ 10%

Adjusted Fe2O3 content = 66 %

It is the WATER here that may be throwing off our reported yield numbers.
The iron oxide powders used as the basis for the analog mixtures are extremely fine. Originally, in an attempt to match the reported chemistry of the L'Anse aux meadows samples, whole wheat flour was added to create the 'organic' component. The physical process was to combine the dry materials, then add water to make a thick paste, roughly the consistency of butterscotch pudding. This was then ladled out on to trays to dry in the sun. It was found that the flour acted like a binder, producing loose lumps of finished 'ore', which also had about the same consistency (porosity) as the natural ore.

How much of the added weight was water?
Although sometimes a sample of the ore used in a specific experiment is pulled off to be completely dried (Usually baked in the gas forge) this 'loss on ignition' (LoI) is not usually recorded. Typical is about 10 - 13 % of the 'as used' weight.

This all occurred to me after the last smelt experiment ('Icelandic' stone block).
Both being somewhat rushed for time, and with an extremely rainy early Summer at Wareham, I had a lot of trouble getting that analog mix dried from the 'pudding' phase. On dry baking a measured sample, it was found that the LoI was actually almost double - at 18%.

I'm not sure exactly how best to apply is considerable difference (10 to 18 % LoI) to the recorded results. One thing would be to consider 'apples with apples', as most commonly the water weight is * not * considered in past recorded results.
- The difference in water weight on this last smelt is then about + 8%
- Reduce the ore weight to 'standard' (29.3 kg x 92% = 27 kg 'adjusted')
- Effects (increases) reported yield (7 kg from adjusted 27 kg = 26 %)


( * )  If you are interested in the long development sequence of our bog ore analog, the easiest way to read the many earlier commentaries is a simple search :
http://warehamforgeblog.blogspot.ca/search?q='bog+ore+analog'

Thursday, July 04, 2019

Stone block furnace

Ryan (L) and Avery (R) - 2/3 through main sequence
Perfect 'chocolate covered cherry' image just as bloom is exposed (Image by Travis Sweet)

Initial compaction : (L-R) Ryan / Rey / Kip / Avery / Darrell (Image by Travis Sweet)
June 23
Furnace related to ongoing studies of possible historic Icelandic systems.
Granite blocks with clay cobb sealing.

Result was 7 kg bloom (about 25% yield)


Readers: I have been buried under a combination of research, project preparation, demonstration, academic presentation, newsletter editing - for the last month.
Up until now, there was a requested news blackout on the upcoming Iceland iron smelting project in August. Expect more entries related to all that, soon!

Monday, May 06, 2019

Introduction to Blacksmithing : May 10 - 12

OPENINGS AVAILABLE

A beginner's program, intended to introduce you to the forge and basic techniques as you make a number of simple objects. Includes discussion of correct hammer use, fast look at materials, history and contemporary work.

Instructor is Darrell Markewitz of the Wareham Forge (over 30 years worshop teaching experience).

Mention membership in OABA for a $25 discount!
Mention membership in SCA for a $25 discount!
Book with a friend and both get a $25 discount!

Details and Register online (Paypal) :
http://www.warehamforge.ca/TRAINING/course.html

Other workshop courses available :
http://www.warehamforge.ca/TRAINING/train.html

Monday, April 08, 2019

Metalworking in Cuba

Gates and Grills in Cuba

On short notice in February, I was offered free shared lodgings at a private owned B & B in Boca de Camarioca, Cuba. (1) I jumped at this, the first real vacation I have undertaken (outside of work related travel) in 30 years.  Boca is just down the northern coast road from the major tourist destination of Varadero, about two hours drive east of Havana. Varadero was originally a purpose built town for foreign tourists , at one time Cubans were not really allowed access. Boca still is where many of the actual Cuban workers in Varadero live. In recent years it has also become a place where ‘middle class’ Cubans have built retirement homes as well. So it is safe to say Boca still does not represent ‘average’ Cuba, but at least is a bit closer than the artificial image presented in Varadero.

Location of Boca de Camarioca, Cuba
It is safe to say that almost all Cubans have a much, much lower material standard of living than almost anyone in Canada. Under the extremely socialist system, everyone is provided with the most basics of food, housing, education and medical. But the quality of those things is definitely the minimal level. Wages against prices is almost alarming, from a Canadian standpoint. (2) Despite this, I found the people generally appeared happy, and certainly friendly enough. (Especially once they found I was Canadian - people seemed to well remember Pierre Trudeau’s support in the 1970’s.)

My idea for a vacation is a semi-active one. I normally like to keep my eyes open, observing as un-intrusively as possible. I spent hours each day, just wondering around, attempting to take photographs. This combination tends to mean not so many images of people, but more of landscape and buildings, with a fair amount of detail, is what I end up recording.

I kept my eyes open for any kind of workshops, but only saw the simplest, honestly very minimal, tools or equipment in use. An old washing machine motor, rope tied to a broken chair, used as a grinder, for example. The only time I saw an ox-fuel set, it was obviously being used for car repairs. However, it is instantly clear that Cubans are geniuses at ‘repair and recycle’. At least a third of the cars on the road were lovingly rebuilt and restored old Chevys and Fords - from the 1950’s and 60’s. Almost all doing daily duty as taxis.
Seen often - a lovingly restored old Chevy
Buildings were constructed of simple (narrow!) concrete blocks, on poured concrete floors, with flat slab concrete upper floors and roofs. Usually set close together on very small lots, with small courtyards at front and rear. (3) Cubans are clearly extremely ‘house proud’, even the simplest home was kept need and clean. ‘Guarantied Employment’ did mean that there were people tasked with street cleaning, but honestly I saw little garbage outside of clearly designated collection points.

One consistent feature was grill work over windows, and metal gates as the entrance through the low wall along the sidewalk at almost all homes. This was the entrance to Lourdes & Leo for example:
Street side entrance to the front courtyard
The use of grills included almost all the windows, certainly ground level, but also on upper floors. (The alternative was windows fitted with wooden slat ’storm shutters’.) Actual glass windows were very uncommon. The typical ‘gap’ in the grill patterns was closer to 6 - 8 inches, suggesting to me they ere intended not to prevent ‘reach and grab’ theft, but to stop physical entry through the openings. As an example, this was the *second* floor covering, on the house next to my lodgings:
The other grills on this house matched the design (this roughly 3 x 6 feet)
Those houses equipped with vehicle drives would also have full height grill-work gates. Most were designed to swing open in two leaves, but some were set to slide sideways. Many of the car gates were backed with simple galvanised steel sheet metal behind the grill work, primarily what looked like a retrofit :
Note the light construction of this two panel car gate
This sample, made of simple embossed sheet attached to the front of some framing, was an exception.
This home (right next to the beach) was certainly upscale compared to others!
One thing that is instantly obvious is : there is no actual forge work here.

- Almost all the grills are made of smaller sized flat stock, primarily 3/4 or 1 inch wide by either 1/8 or 3/16 thick. The white grill seen above is unusual in that it was made from 3/16 round rod, a material I only saw used a couple of times.
- Most all the grills were joined by welding cut bars, or simple cold bent scroll elements, together.
- One standard method is to twist the flat bars at 90 degrees at an intersection, then twist back to ‘edge on’. (Allowing for secure and simple welding)
- All the gates were painted, but in brighter primary colours. Green being the most common seen. Curiously, I saw hardly any use of black paint.
- Terminals were most commonly simple bevel cuts, or just left as square ends
Detail, note terminals, reason for the paint!
All of this taken together, suggested to me that the range of metal stocks available was extremely limited, stick welders in use, with only simple hand tools employed.

But within these extreme limitations, and what obviously are great cost constraints, there is clearly a good sense of design from these metalworkers.

This is an overall view of the detail above, which illustrates exceptional design inside the limits imposed.
At entrance to a small apartment building
Shows flow of lines, and balanced mirroring of shapes, from the upper to the lower sections. A balanced symmetry down the centre.
Elements from one section carried to the next - but not simple repetition of design.
Now I freely admit that my sample was confined to a very small area, and limited time. During my week long stay, I only saw one building from the ’Spanish Colonial’ period, and it in very rough condition. (Cuba’s ‘European Settlement’ goes back to roughly 1500 - but ‘Pre-Revolution’ elements are not well represented today.)

Still, I think the work I did see, even if in a relatively affluent area by Cuban standards, certainly represented the creativity of the Cuban metalworkers, despite serious restrictions on starting materials and limited tools.
 

1) Highly Recommended !
Hostal Lourdes & Leo / hostal.lourdesleo@nauta.cu
This trip, the cost was roughly $28 CDN per night, for living room, one bedroom with two queen beds, small kitchen and tiny bathroom. Nice beach 5 minutes walk, 100 m from the main road. Wonderful hosts!

2) One example : Although school teachers are notoriously badly paid - even by Cuban standards, the cost of a simple pair of foam ‘flip flops’ was equal to roughly  * one week’s * wages for a high school teacher (paid roughly 25 CU / month).

3) I did see a reasonable amount of ongoing construction, mainly additional floors being added to existing homes at what seemed a snails pace. I found out that that same teacher’s monthly wage would only pay for 4 bags of concrete. The building blocks where commonly 4 inches wide, by roughly 18 inches (or more) long, with some only 3 inches wide. I rarely saw any metal re-enforcing in place in wall construction. Given occasional hurricane force winds, most certainly the slab roofs would lift, walls collapse - to the destruction of those living inside. This is in fact what happens on a regular basis in Cuba.
 

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

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