Period bottle glass number two

4.6.17.2

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.

4.6.17

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.

Something far less useful

Microwave 1

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.

Microwave 3

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.

Microwave 2

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!

I think I have just passed my Kimberley Points ‘A’ Level

Kimberley Point A level

I can’t seem to stop myself at the moment. This was a large piece of 6mm plate glass found at Chorlton Water Park yesterday. It was from near a blown down tree but I think the glass is modern. I divided it into two halves (using a glass cutter) so as to have two goes. This is the result from the first half. I followed the ‘one side, one face’ rule, with a little bit of hard hammer shaping for the base to get rid of big bits. Mainly though it was the large copper pressure flaker and the abraiding stone that has been used to get it into shape. This involves getting a series of really nice invasive removals, and a good edge, and then abraiding heavily in the areas that need reduction. Repeat until required shape is achieved. When close I shifted to my smaller copper flaker.

Materials

This Kimberley Point is large, something like 153mm long, 29mm wide and 6mm thick, and not disimilar to some of the Manchester Museum larger examples. What I discovered is that it is quite stressful when you get to the later stages, as mistakes can have big consequences. ‘Koalaboi ‘ on Bushcraftoz.com told me that he found making “the very fine point at the tip is excruciatingly difficult!”. Up until now I have found that process relatively OK, until working this large point. A lot of time and effort is invested and then it becomes quite stressful because the tip is so thin. In relation to these needle type tips, not all examples have them and I suspect larger examples like this do not because they were used as knives. I have put one on this example but need to check the literature again. Anyway, right shape, method, retouch pretty invasive and similar to museum examples. This evening I am feeling pretty pleased with myself!

pleased-with-myself.jpg

On glass quartering and pressure flaking

over-the-range.jpg

Following the advice of Kim Akerman I bought a copy of the above book, as it details the process of quartering a bottle using hot wires. However my book was a later edition to Kim’s and the page numbers differed. Anyway, the section relevant to this enquiry is at the beginning of chapter eight, regardless of edition. Apparently a long wire was heated in a fire and when ‘red hot’ twisted around a bottle base. This resulted in the base dropping off. The same procedure was then applied to the neck resulting in a glass tube. Finally the red hot wire was used to quarter the tube resulting in four equal sized glass preforms. In a previous post I discussed my hard hammer technique. Obviously, if this hot wire method is used no hard hammer work is necessary.

This section of the book also has useful details on the bodily approach to pressure flaking. An anvil stone is used and the knapper is seated with one leg tucked behind, and the other leg stretched out along the anvil. Some paperbark is placed upon the anvil to act as a cushion. The lengths of no.8 fencing wire used had both diamond and chisel tips, and these tips were regularly sharpened on the anvil stone. The wire was held “as we might hold a stick tight in the hand” (Idriess 1951: 47) with the fingers facing uppermost and the business end of the pressure flaker facing into the body. Leverage was generated by the “thumb and palm and arm” (ibid).

pressure flaking position

The glass would be held flat on the cushioned anvil stone whilst the pressure flaker was placed “firmly against one-half the width of the edge” (ibid). This would seem to be an important detail in that the edge is at approximately 90 degrees, as opposed to bevelled. This 90 degree approach allows flaking to be applied to each face equally. I need to play with this in order to understand it better. The knapper then “levered downward with a quick, short thrust, and a long, deep flake of glass flew out” (ibid). The longer flakes came from the convex (dorsal) face, whilst smaller removals were taken from the concave (ventral) face. Each edge was worked in turn. Through this process the piece was first flattened and then shaped and then finished. There is plenty to play with here and it has stimulated some thoughts upon ‘pulling’ as opposed to ‘pushing’ flakes off, and also on the relevance of ‘impulse’ versus slow and steady pressure. Ion Idriess has given me some ideas to test out.

An interesting learning experience

Continuing with fragments from the same porcelain cup I selected a side section and so again the curvature needed to be managed. A fair amount of material had to be removed and I found myself intuitively using a new technique when shaping the fragment using the hard hammer. 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. The additional strategy I found myself using was to support the platform with my finger. This leads to me hitting first the platform and then my finger. The flake is removed but it remains in place (see photographs below). I think the finger acts as a shock absorber thus reducing the chance of the flake fracturing randomly. In any case, it worked really well. The interesting thing is that I know where this strategy came from. If you view the video of Karl Lee making a scraper he does exactly this action at 1 minute 36 seconds (https://vimeo.com/80064183). I produced that video well over a year ago and have only now found myself consciously doing this.

supported flake removal hard hammer method

Overall this means that my rough-outs are becoming more controlled even when the hard hammer is relatively large.

roughout

From there I used the copper pressure flaker again to start imposing more of the shape and thickness wanted. When I was happy with that I was able to notch the edges which as can be seen, are getting better. This material holds the notches well.

number three ventral

number 3

The red section is the remains of the transfer pattern that was originally decorating the outside of the cup. Also, I am starting to remove more of the dorsal surface with my invasive flakes. This example is 67mm long, 31mm wide and 7mm thick.

‘Dishwasher Safe’ Kimberley Point

ddorsal

Today I experimented with a new material. This Kimberley Point was made from the base of a broken porcelain china teacup. It had one slightly convex, and one slightly concave surface and presented similar problems to beer bottle bases used previously. It was surprisingly enjoyable to work and consequently I am quite taken by it. It is harder than glass and seems to hold the notches better. I am not sure whether to make the base more symmetrical or to leave it as is. It is 64mm long, 36mm wide and 4mm thick with retouch penetrating between 5 and 10mm into each face from the margins. The ‘Dishwasher Safe’ title comes from the text left on the ventral surface.dventral

Bottle glass Kimberley Point

bottle glass dorsal

This is my best Kimberley Point yet. It is made from a side (and therefore curved) section of a beer bottle. I have followed the published methods more closely this time in that I used a small hard hammer stone to approximately shape the piece, and then heavy abrasion and pressure flaking to finish it. Finally, a small and narrow ‘watchmaker’s’ screwdriver was used to produce the serrations along the edge. I generally worked one edge and face at a time and some of my thinning flakes penetrated half way across the dorsal face. The shape is a little idiosyncratic and I like it like that. Because these points were hafted using a blob of resin they could be easily aligned to accommodate idiosyncrasy. It is 56mm long, 31mm wide and about 5mm thick and form wise is based approximately upon a published outline illustration (Akerman and Bindon 1995: 92 Fig 4. Bottom row number 4.). Because this was formed from the side section of a beer bottle managing the inner curve was a primary problem. Akerman and Bindon (1995: 93) state: “Broad examples produced from sections of glass bottles usually have relatively short scalar retouch on the concave face“. As can be seen below that is reflected on this piece. Because of the curve it is not possible (or desirable) to get long invasive flakes across the inner surface.

bottle glass ventral

So size, form and method of production are all consistent with published material and I like the aesthetic of this one. However, I am still using my copper pressure flaker, and so hafting my no.8 wire will improve things. Also, there is an aboriginal method of dividing a bottle using heated wire. I want to try this and today ordered Over the Range by Ion Idriess in which he outlines exactly how this process works (pages 59-62). Next Wednesday Elizabeth Healey and myself are going to the Manchester Museum to examine the collection of six or so glass and stone Kimberley Points. I am looking forward to seeing first hand how an indigenous knapper has dealt with these same problems.