15 October 2014, Preparing sandcasting molds for medal casting at Ubaldo's

NAME: Jenny Boulboullé, working partners: Diana Mellon and Pamela Smith
DATE AND TIME: 15 October 2014, 9:45 am - ca. 2pm
LOCATION: Chandler Lab 260
SUBJECT: Preparation Iron mold sand casting of medal patterns by Pamela, Diana and Jenny

Diana prepared the sand and Pamela took notes by hand, later on Jenny took over from Pamela and Diana.

Sand preparation for 3 medals in an iron mold

Diana started out by mixing (with hands):
5 cups sand
½ sal ammoniac water
2 tbs Brandy

Diana carefully crumbled sand in – sand felt like feta cheese which has been drained. When pressing it can be formed into a ball, but still crumbles easily.
Tonny Beentjes advised to check sand by throwing a ball of it up and catching it without crumbling it.
Sand dries noticeably as it is crumbled.
When sand is well mixed, Diana starts to packing it slowly around the edges of the patterns. She carefully packs and presses the sand around the medals and into the corners of the frame. She makes sure that the medals are secured in the same place and do not shift. When covering the fronts of the medals, Diana tried to crumble the sand more finely and carefully pressing it into the impressions of the medals. This was difficult as one of the medals was not flat on the back (Pamela’s medal which was placed below the other two medals in the iron frame), so she had to be careful to press the sand onto it without breaking the plaster model.

We needed more sand to fully cover up the patterns. So we made a new mixture:

3 cups of sand
½ cup of sal ammoniac water mixed with 2 tbsp brandy

We added another ½ cup of sand and sprinkled some extra water mix onto it.

When we finished filling up the iron mold we smoothed the surface with a big knife. We turned it around and ounced wholes in the corners and cleaned the contours and backsides of the medal, so that the backsides and contours were not covered by sand anymore. We put the other box mold half on top of our filled box mold and dusted the medals with charcoal powder using a brush. Jenny took it over from here from Diana and Tonny also helped with the next steps.

For the backside we used a sand mix that has been prepared by Jef (thank you Jef!) The mixture consisted of approx.
6 cups of sands
ca. 1,5 cups of water sal ammoniac mix
2 table spoons of brandy

We carefully pressed the sand on the backside of the medals and into the corners with holes until well covered and all compactly sealed. We further packed sand on the backside of the medals until the medals were fully covered and the iron mold was filled up so much that the surface became a little concave. In this final phase I (Jenny) ran almost out of sand, I got a bit more sand that was left over from Raymond and Jordan (well mixed sand was a precious good in our lab as we had a shortage of pulverized sand and it turned out to be a tricky task to prepare the sand well, so we are very grateful to our donors). This sand was actually much wetter than the sand I used to pack up my medals, but it worked very well to smooth the surface. As a final step we first hammered the sand and then Tonny made the surface straight and smoothed it out with a big knife. I sprinkled a bit of sieved not wet sand on the top of it to make the surface drier. Tonny parted the mold halves and we got the medals carefully out. The contour from Pamelas medal was not perfectly cleaned, but we managed to get it out. Finally Tonny cut and scraped the runners out, some sand stuck on the other side, but that was not problem as it did not effect the medal patterns.


Some observations:
Firstly, writing up our hand written notes a few weeks after the experiment turned out to be a more difficult task than I had expected, even though Pamela and I took detailed notes and I thought I just need to tick them over into a word file, there were several passages where my notes appeared ambivalent to me and it took me some effort to try to remember what I meant by that. E.g. I had made a note of how much sand we had used in total, but when I reread my notes I saw that the different mixtures did not add up to that total amount, so I decided to only write up the separate mixtures. I also realized that it took me some effort to visualize the working process again and without looking at some photos I would not have known anymore when we turned our first box halve around and proceeded to rework the backsides of the medals.
I remember that I had rich impressions of how the different sand mixtures felt, but writing that up retrospectively was more difficult as I only wrote down in my notes that the sand was drier or wetter.

Unfortunately part of the photo documentation that was taken with an iphone got lost.

One of the learning experiences I got from this experiment is that it really is sensible to take as a golden rule to write up field notes and upload photomaterial the same day of the experiment.

See below for images from casting our mold at Ubaldo's.

https://www.flickr.com/photos/128418753@N06/15762994701/
https://www.flickr.com/photos/128418753@N06/15579017679/
The silver casts next to the plaster pattern by Pamela Smith and Jenny Boulboullé, as you see the impression in the cast is not very pronounced.

https://www.flickr.com/photos/128418753@N06/15380022787/

Silver cast of NP medal by Jenny Boulboulland. The cast did not go well, because the mold was still too moist, which caused the silver to turmoil while pouring and causes the bubbles, spikes and bumps in the cast.


https://www.flickr.com/photos/128418753@N06/14945558863/
The open mold halves after the cast, you can see that the patterns have been severed by the violent cast due to too much moisture in the mold.

Kiln firing November 2014

One of the most powerful tools that we have purchased so far for historical reconstructions of recipes from our manuscript is a “kiln”. A kiln is a furnace or oven for burning, baking, or drying, that can reach very high temperatures to calcine materials or fire pottery (OED). We are especially interested in using it for calcining, the process of reducing materials to ash by strong heat. The author of our manuscript gives several recipes or experiments for which calcined materials are used, such as oysters burnt to ashes, but also ox hooves and even human bones!
Our kiln, a Paragon Dragon, has just been delivered and installed and this has been our first week of getting acquainted with this powerful tool. We are still in the process of naming it, this week’s favorite is ‘Vulcan’, which goes well with my first impressions of a ‘fire breathing dragon’, who now lives in our lab and whose volcanic capacities we are trying to understand and to control. Operating a kiln turns out to be quite a challenge. Getting a feeling for our kiln and learning how to control and work with her makes me think of taming a lion, though its in essence a simple tool - not much different to a domestic oven, but endowed with a much more fiery capacity (almost 5 times the maximum of a regular oven, our kiln can go up to maximum temperature of 2350 Fahrenheit).
The OED provides us with a working definition of the kiln that is very similar to the one used in modern ceramics industries, where a kiln is basically defined as a “high-temperature installation used for firing ceramic ware or for calcining and sintering” (Dodd and Murfin 1994:176)
It is important to note that kilns have a very long history - covered kilns have been dated back to 4000 BC, but the use of open or semi-buried examples appears to go back as far as 8000-4000 BC.⁠1 However, the question “what is a kiln” would probably be answered differently by users, engineers or scholars, depending on the research or user context (Rice 1993: 2).Defining what a kiln is, can for example turn out to be a problematic issue for archeologists who are faced with scarce remains from which to reconstruct the forms and use of pre-historic kilns; moreover, when dealing with “the long developmental history of prehistoric kiln forms”, researchers face the problem that they rather work with fuzzy typologies than clean-cut categories (Rice 1993: 2).

For our historical reconstructions of early modern experimental processes that involve the use of calcined materials for metals casting in sand,it is important to note that the term “furnace”, which we come across more frequently in primary source texts and recipe books, is often used interchangeably with “kiln”. Vannoccio Biringuccio for example provides us with detailed descriptions of building furnaces or “kilns” for firing bricks (Biringuccio: 400) and calcining lead and tin in what a sort of kiln what he calls a “reverbaratory furnace” (Biringuccio: 394).
In our manuscript the French term “four” can mean different things, such as “furnace”, or “stove” according to context; assumably our author refers to some sort of “kiln” or “furnace” when he mentions high temperature installations used for calcining materias (French: “calciner”).


Vulcana!

First Fire Trials field notes

18 November 2014
Name: Jenny Boulboullé, further present Donna, Emogene
Location: Chandlers Lab 260
Weather: strangely hot with more than 12F for this time of the year.

First loaded firing trial:

Three terracotta plates full of oysterdust/small pieces, uncovered
Programming firing from room temperature to 300 at fullspeed, hold for 30 minutes, firing it up to target temperature of 1400, which we never reached, started to smoke and smell heavenly at 500

Second trial 25 November
One terracotta plate with small pieces of crushed and dried oysters, covered with an empty terracotta plate
Ramp hold programm:
72 room temperature
Fullspeed to 1500
Hold 10 minutes
No controlled cooling down programmed

Within 30 minutes, our kiln reached 1000F and within an hour he reached target temp of 1500F. No smoke and minimal smell today.

Wednesday 26 November 2014
Name: Jenny Boulboullé, further present during this experiment Yijun, Michelle, and from noon onwards Donna. Diana joined us for some time in the morning and early afternoon.
Location: Chandlers Lab 260
Weather: cold rainy in the morning, snowy rain starting at about 10 am!

Third firing trial with Vulcana today. 26 November 2014
(A discussion about our kiln being a he or a she ended in transforming Vulcan into Vulcana, though we are not sure yet that she wants to commit herself to one sex, perhaps she prefers a transgender identity?)

We started at 9.15 am in the lab. Yijun and me went through the protocol and discussed the temperature accelerating rate and the appropriate container. Eventually we decided on firing the hove ox bones on a terra cotta plate instead of in a cast iron pot, because terra cotta plates had also been used by the research group from that article on bone calcination that Yijun’s group had found. From this article, we also took over the protocol for the firing accelerating temperature. Moreover, we had by now ample experience with cracking terra cotta plates, which appeared to be a reasonable calculable risk, whereas we did not really want to imagine what to expect from a potentially exploding cast iron pot…

Firing protocol:
Accelerating rate from room temperature to first target temperature: 1100F/hour
Ramp hold at first target temp 400F for 2 hours
Accelerating from 400F to 1500F again at 1100/hour.
Ramp hold at second target temp 1500 1 hour.
End program (no controlled cooling down)
See for time record of firing process time monitor sheet.

All in all we expected the firing to last for about 6 hours.
‘Vulcana’ performed today’s firing marvelously. She certainly has a preference for high temps. At about 600-800 she seemed to groan and grumble somewhat, puffing smoke and smelling intensely. We still are in the process of getting to know her and taming her, but we are getting better in anticipating little outbursts from her side, and calculating the risks in beforehand, such as another broken terra cotta plate today that cracked probably sometime when accelerating from the first target temp (400F) to the final target temp at probably around 800F. But from 900 F upwards our kiln purred like a happy cat, stopped smoking and held her temps excellently. After staying on 1500 F for an hour, we let her cool down and at about 800F we donned all proper PPE and Donna carefully took the cracked bones plate out of the kiln and put it on three pipes on the lab counter. All in all, it took us eventually until about 5 pm to cool Vulcana down again.


1 History of ceramic kilns. 1984. Ceramica y Cristal 23, (91): 35-37, http://ezproxy.cul.columbia.edu/login?url=http ://search.proquest.com/docview/24233018?accountid=10226 (accessed November 24, 2014).