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.

Neolithic 3

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.

Neolithic 2

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!

Making an ‘Ishi’ type pressure flaker.

Ishi was a Native American from who much of our understanding of the practicalities of pressure flaking has been gleaned. Within our twice weekly knapping sessions Nick Overton has raised the bar by introducing the use of soft iron nail pressure flakers, similar to those used by Ishi. This is a version of the same with a replaceable point. It is easy to make with total material costs of less than £2.50. Tools needed are a saw, chisel, hammer, large nail and a gimlet. Time wise it takes about half as hour. Materials needed are a bean pole (22mm wide, 75p), two copper end pieces (internal width 22mm, £1.40), one cut flooring nail (60mm long, can’t remember how much, they come in bags of about 20).

1. Use the saw to cut a section of the bean pole to a length that will be comfortable in your hand (perhaps 140mm). Then use the hammer and chisel to split it in half.

Pressure flaker 1

2. Use the cut flooring nail to gouge out a groove on both pieces to fit the nail, and then use the gimlet to bore a small hole on one side to accommodate the head of the nail. Then insert the nail.

Pressure flaker 2

3. Put both pieces together and modify to make a tight fit.

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4. Use the hammer and large nail to punch a hole in one of the copper end pieces and insert it over the nail to hold the pieces of bean pole together.

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5. Stick the second end piece on the other end. These two pieces need to be tight and so some trimming or padding may be needed. When finished the nail needs to be filed to a point and when used, kept sharp. The main benefit of this design is that as the nail gets filed down it can be replaced easily with a new one. When you make one of these, by default you have to then start making Ishi Points. Perhaps that will be the next post!

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.

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!

A more detailed reduction sequence.

mm ventral

I am currently revisiting the literature before we start on our collection of antique bottle fragments. In particular a 2002 paper called “Weapons and wunan: production and exchange of Kimberley points” (Akerman, Fullager and van Gijn) as on page 22 it outlines a very detailed but concise reduction sequence. Essentially, for bottle fragments the most energy is spent flattening the curved inner surface. Consequently this inner face is flaked from either side, in turn, until flat. The above photo is of a point within the Manchester Museum collection and illustrates this description excellently. This process ‘sets up’ the upper or dorsal surface for the next phase of removals. This involves a single series of flakes being taken from each edge.

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This is what we see on the dorsal face above, and I think this is one facet that gives these points their characteristic look. Only then is the edge serrated or notched and the tip worked. This example doesn’t have the needle like tip and is what gave me the notion that larger ones may have been used as knives. Returning again to the ventral surface, what we can see in the photo is an almost plano-convex cross section as opposed to lens shaped. Finally, it would take an aboriginal knapper about 45 minutes to make a 200mm long point. This would be a very large point indeed. The overall approach outlined above is the one I am going to take with our period materials, although it may take me a little longer than 45 minutes 🙂

Akerman, K., Fullagar, R. and van Gijn, A., 2002. Weapons and wunan: production, function and exchange of Kimberley points. Australian Aboriginal Studies, (1), pp.13-42

You need to be able to trust your platforms

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This post is about pressure flaking, what I am learning about the process, and how this learning is helping me to improve. The main learning outcome currently is summarised above: you need to be able to trust your platforms. So what does this mean in practice? To explain, it is useful to reiterate my own understanding of what constitutes a platform from a previous post (An interesting learning experience):

Primarily,  I identify the area of the fragment that needs reduction. I then focus in to find bits that stick out. These points will be inherently weaker due to the lack of support on both sides. Consequently these points provide useful platforms with which to remove invasive flakes. If this platform sits above the centre-line of the edge I will flip the flake over and use it to remove a flake from the dorsal surface, if it sits below then I will use it to attack the ventral“.

So fundamentally I am identifying an inherently weaker area to target with the aim of thinning the piece. The platform is simply the area to be pushed into with the point of the pressure flaker. Heavy abrasion of the margin effectively removes any weak areas and establishes a strong platform. This seems tautologous in that I am identifying a weaker area to exploit, only to then strengthen it. However, it needs to be strong enough for me to apply pressure effectively in order to achieve the aim of removing a flake. Failure to prepare the platform can lead to crushing of weaker zones when the pressure is applied. This acts as a shock absorber dissipating the energy being applied and compromising the flake production process. I am therefore learning that the issue is not me becoming stronger, but applying my strength more accurately and cleanly into a prepared area of structural weakness. The connection between the pressure flaker point and the platform needs to complement the angle through which the pressure is to be applied. So far so good.

However, how I began to understand this is of interest. I am currently using glass and aiming to ‘push’ flakes across to the centreline of the artefact. An inhibitor to pushing into the margin with real strength is the possibility of the pressure flaker slipping and shards of broken glass being pushed into your thumb. This second possible outcome inhibits the confident application of as much pressure as possible into the platform. Conversely, the recognition of a constellation of factors under my control: recognising an area of overall structural weakness; preparing a strong platform; using a sharp pressure flaker; understanding the required angle; all of these control opportunities are giving me confidence that I will now achieve the former, rather than the latter, outcome. This confidence is now allowing me to really apply pressure and begin to push off longer flakes. The above understanding of how to make it work is giving me confidence to push in hard, and to make it work. A virtuous cycle is emerging. I already had these conceptual knowledge components, but I realised today that my bodily confidence has increased along with the knowledge that my platforms (through preparation) will behave predictably under increasing pressure. I am learning to trust my platforms.

pressure flaking