Neolithic Milk of Magnesia interlude.

I had the opportunity to have a wander around Chorlton Ees one morning last week and came home with quite a few pieces of old glass recovered from the roots of fallen trees.

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This lovely blue piece in particular caught my eye and I like to think it is the base of an old Milk of Magnesia bottle.

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As you can see it is chunky and I wasn’t quite sure how well I could reduce it. This is because it is both narrow and thick and I was worried that I may run out of width before it was adequately thinned. Anyway, today has been a beautiful day here in Manchester and I got to spend a couple of hours outside playing with it.

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I am pleased with the result. It has become a Neolithic leaf shaped arrowhead, similar in proportion to some of the stone examples I have seen. The edges are sharp, the tip is good and it is fairly symmetrical.  What really makes it stand out though is the lovely blue colour. When Nick Overton sees this photograph he will immediately focus upon the very, very small section of original surface left in the middle. All I can say Nick, is: “when a pickpocket meets a saint, all he sees is pockets!”.

 

A test run for the Ishi Stick, and a ‘tough break’

Since getting together with John, Rob and a few others for our regular knapping sessions, pressure flaking has become a bit of an obsession for me-in particular, working pre-cut glass slabs into points of various sizes.  Key to this is taking a good first set of pressure flakes, to remove all of the original surface-an end result that is ‘fully invasive’ has become somewhat of a holy grail for me over the last few weeks. To that end, I decided to make an Ishi stick out of a chair leg John donated-a number of the knappers on youtube, including palaeomanjim, seem to use them for their larger pressure flake removals, and the general idea is the longer handle allows more power to be applied, thus removing longer flakes.

The construction of the Ishi stick is very similar to the Ishi style pressure flakers John discussed a few posts ago-I split the lower part of the chair leg, cut a groove for the nail, and carved a collar to locate the copper cap, and another recessed section, which I bound with string to secure the whole thing. Initial attempts to use the Ishi stick were a little shaky, and overall it felt a little odd, as the long handle runs up the forearm and braces the wrist.  However, once used to it, it allowed a more controlled application of power, and resulted in some excellent long pressure flakes.

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Detail of the Ishi stick at the business end

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The Ishi stick (top) and the Ishi style pressure flaker

However, as the often uttered phrase goes, with great power, comes great responsibility.  In this case, a responsibility to pick the correct platforms, and a responsibility to control the removal process and avoid unnecessary force.  On this first outing of the Ishi stick, it was a lesson I learnt the hard way, breaking every piece I started. But, there is a lesson to learn in every mistake-on reflection, all of the breakages occurred at the same point in the point-making process. I had successfully removed the plate glass surface with the first pass of pressure flaking using the Ishi stick, and I had returned to take a second set off, using the high spots left in between the pressure flake scars taken in the first pass as platforms. I used both the Ishi stick, and the Ishi style pressure flaker for this stage on different pieces, but both resulted in the piece ending in two bits.

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Good invasive removals from the blank, but both broke in the middle

At this moment in time, I have yet to decide whether this is because I am putting too much force into this second set of removals, because my technique is exerting too much ‘bending’ force on the piece (exerting a force along the axis of its thickness, as opposed to across its width), or whether the pad I am using for pressure flaking, with a groove to allow a free pressure flake removal, is not offering enough support.

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My pressure flaking pad and one of the broken pieces. Is the groove in the pad too big to support a piece this size?

So our next knapping session on Thursday will see a new three-fold approach: 1) Removal of the first set of flakes using the Ishi stick and pressure flaker pad. 2) Good platform preparation (or re-preparation). 3) Removal of second set of pressure flakes using the Ishi style pressure flaker, and a new pressure flaking pad with a smaller groove, so as to offer extra support.

As John said at the end of his last post, I am sure we will be making a few more of these-for me, it’s fully invasive or bust!

A second point from the second preform.

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I was more cautious with this one and it turned out longer. I tried to stick to my method, ventral first, then dorsal, then the point, however the angle of the edge face made me improvise a bit. I am pleased with the needle like point, and am going to arrange to go back into the Manchester Museum to compare and contrast. I think the key difference between mine and the actual points may be thickness and edge angle. Let’s see. 9-6-17-2.jpg

The next post will be about home made pressure flaking tools, as we have been innovating in our twice weekly knapping get-togethers.

Period bottle glass number two

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This is one half of a piece of period bottle glass recovered from Chorlton Ees. My aim this time was to make a larger point and maintain some of the lettering on the dorsal surface (see Foraging for early 20th Century glass and ceramics).  I used a glass cutter to score the inner concave ventral surface of the larger piece of glass, and then tapped the dorsal convex surace with a hard hammer. The large piece split cleanly into two useful preforms, one of which you see here. I then started to work on the ventral surface of the margins to produce a steep edge angle. This would allow me to flip it over and start using the newly created steep edge as a platform for penetrative flakes. The aim of this penetrative flaking was to flatten the convex curvature on the ventral face. I was able to straigten and steepen the margins but was not as systematic as I could have been. Working around a thick area semi-disaster struck! break.png

I called it a day in the lab and took both pieces home, and the following day finished it off. The ‘A’ is a useful landmark on all three photos and gives an insight into the degree of reduction. I am getting a feel for this thicker and uneven material and was able to avoid a large internal bubble, which is why the base has remained relatively unworked. The end result isapproximately 76x26x7mm and pretty well flattened on the ventral side.

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After the above photograph was taken I serrated the margins. My main learning from this piece is to be systematic in my reduction sequence. If my edge steepening had been more consistent I would have achieved a longer point. I am making some points for Eleanor Casella’s teaching collection and I think this can be one of them as it has an interesting provenance and biography, as well as being an aestheically pleasing example.

Using old glass

bubble glass

The above Kimberley Point has been made from an old piece of glass, the flat side of a Camp Coffee bottle. My aim was to retain the raised letters that spelled ‘chicory’ but it was not to be. If you look closely it is clear that there are bubbles in the glass and the section on the bottom left is the edge of one large bubble. These voids meant it was necessary to continually adjust in order to manage them, hence the small size.

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This second point is made from a side section of an old glass beer bottle. This is similar to one seen in the Manchester Museum and the main issue here was managing the curve and the variable thickness of the glass. The proximal section on this piece was much thinner than the distal. I am happy with it as a point, but in order to get that feeling of sharp serration on the margins I need to get the initial invasive flakes deeper, to reduce the angles. So whilst the microwave turntable presented its own set of problems, the transition to using old glass has highlighted some interesting issues that need to be considered when attempting to make these points as aboriginals did: uneven glass thickness; managing a transverse curve on longitudinal section; and accommodating bubbles in the glass. All in all an interesting process.

Hard earned

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We have been having regular Tuesday and Thursday evening ‘knapp-ins’ for the past few weeks. Between the three of us we each gravitated towards different materials. Nick focused upon the remainder of the thick microwave turntable. Rob brought in some Langdale Tuff, a volcanic material with a fantastic texture, and I brought in a bone china plate. This bone china is hard, and very difficult to get long removals from. It really does seem to be a case of heavy abrasion to get incrementally longer removals, only to abraid again to get a bit further. Each of the above removals was hard earned.

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Both Koalaboi and Nick recommended having a look at Paleomanjim’s Youtube channel. He uses a number of methods depending upon source material, but to maximise flake length he combined two approaches. Firstly he used abrasion and removals to create a steep angle that can be used optimally for one face only. He also used a pad with a channel cut into it. He has identified that having this void below the flake being removed means that it has absolutely no support, and thus comes off cleanly. Even small amounts of support (contact) can lead to step fracturing. This makes sense, although it doesn’t seem to be reflected in the Kimberley Points literature. Once optimal length flakes have been removed from one face, the the margin in prepared so as to remove optimum flakes from the second face. This process is primarily aimed at thinning and creating a lens like cross section. I have a couple of fragments of this material left, and so I am going to test out this steep platform method this Tuesday evening.

Something far less useful

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On Thursday evening I had a knapping session with Nick Overton and Rob Howarth. The ‘dish of the day’ was a toughened glass microwave turntable found in Nick’s garden. It took me a couple of hours to be able to get beyond the raised edge that was the outer lip of the turntable. As such it has been a masterclass in working angles and really got me thinking. Following the published methods is very interesting and the previous post focused upon managing the curve on bottle glass. However, this toughened and lipped turntable presented a different set of problems. It has made me think about the difference between aboriginal examples with plano-convex, and those with lens like cross sections. I wonder if plate glass examples like this lead to lens like cross sections because both faces are worked in a similar manner? I finished the above preform off this morning.

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As can be seen, it has reduced in size considerably, and this is a reflection of working to get increasingly shallow angles and therefore longer removals.

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This image shows better the degree of removals from the surface, and I can now report that the really long removals are in fact a combination of well prepared platforms that allow pressure to travel along a shallow surface angle. These shallow angles come from transforming a perpendicular edge into a steep angle, and then using this steep angle as a platform to take another removal that creates a longer shallow angle one. None of this discussion is new, however I am beginning to be able to apply these aspects systematically within a meta-approach to either plate glass or bottle glass. I am making practical sense of the textual descriptions that do not really separate out how these processes change (or remain the same) depending upon the materials used. It would be useful now to revisit the Manchester Museum examples to see if I can recognise if the source material was either plate or bottle glass, and if this actually does reflect a plano-convex or lens like cross section. Anyway, to para-phrase Nick, it has been immensely satisfying transforming this microwave turntable into something far less useful!