Introducing the APT Petro-Lab

Affordable, Practical and Transportable Petrographic Laboratory

Original post on the TwoRains Blog.

Hi again – it is Alessandro, your neighbourhood ceramic specialist. In a previous post on Indus Ceramics (link here) I mentioned some of my daily tasks as part of the TwoRains research project in Cambridge: amongst them, ceramic thin-section petrography, which I am using to study aspects of ancient Indus societies, crafts and technologies.

Between excavations in the field and laboratory analysis, there is an intermediate stage where I identify the most suitable vessels for further study and collect samples, including thin-sections and powder from ceramic vessels. This can be quite an engaging and complex task, particularly if you are not allowed to move antiquities out of a country and bring them to your laboratory. With this in mind, we asked how would we go about producing 30 microns’ thick sections of ceramic vessel fragments in the field? Well, I have developed my personal portable laboratory, and I am going to share it with you. Take your goggles, lab coat and gloves (and risk assessment form!) and get ready for the dirty work of building your DIY Petrography Lab!

Thin-section production follows on from a preliminary documentation and macroscopic analysis of ceramic materials, and falls into five main stages: (1) cut a small section of the selected sherd; (2) impregnate it with resin; (3) grind and polish the impregnated chip; (4) bond the chip to a glass slide; and (5) re-section and grind the sample. All of this is easier said than done, and the right tools can be quite expensive. This is not the first attempt to make a portable thin-sectioning lab (see disclaimer below), but I needed something that would fit the budget of a PhD researcher. Therefore, my first key word is ‘affordable’.

The second key word is ‘practical’. I tested the laboratory in different countries (e.g. Italy, UK, India) and under different climate conditions, and I could successfully produce several hundred thin-sections in a relatively short amount of time.

The third key word is ‘transportable’, which is critical for a petrography lab that has to be moved between countries. Ideally, a portable lab should fit in a small or medium sized case for it to be functional and movable between countries, archaeological sites and excavation archives without having to hire an international moving company. Devices such as the PetroThin Thin Sectioning System are ideal for cutting, grinding and polishing thin sections, but they are very big and must be replaced by something smaller and possibly cordless so that they are capable of functioning under circumstances where electricity is not always guaranteed.

The first portable kit that I put together was tested in India in 2016, but it was a relatively slow to use, and I produced a new and improved version in 2017. A list of essential tools of the APT Lab v.2, which you can easily find at a trusty DIY shop or on well-known web sites such as Amazon or eBay, is as follows:

Cutting and Re-cutting:

• Dremel® cordless (8200);
• Dremel® diamond cutting wheel (sc545);
• Tile cutter (optional);
• Plastazote foam;

Resin Impregnation

• Electrical Single Hot Plate/1500 Watt;
• Thermometer Analogue/Bimetal;
• Tinfoil;
• Tweezers;
• Sticks;
• Plasticine or modelling clay;
• Disposable paper cups;
• Syringes;

Bonding Chip to the Slide

• UV 15 W Black Light;
• Rack/grid;
• Frosted Microscope slides;

Polishing:

• Tempered glass for hand polishing;
• Sandpaper (grit: 240 and 600);
• Carbide paper and powder (grit: 600).

Dremel® cordless (8200) and tile cutter (optional) are the crucial tools here for cutting and re-cutting ceramic sherds. You can shape a solid support for cutting sherds and holding the drill by modelling, for instance, a small block of plastazote foam. The UV black light is NOT used for organising evening festivities in the field, but for quickly drying the optical glue, which is used for sticking the impregnated chips to microscope slides. Similarly, the electrical hot plate – which, again, is not meant to be used for cooking delicious exotic delicacies – but for heating up ceramic chips before impregnation, to reduce the possible formation of bubbles and to ensure better impregnation of the resin. The plate can be covered with clean aluminium foil, the temperature kept very low and checked with the thermometer to make sure that you don’t burn your pots.

These tools work in combination with chemical substances, such as epoxy resin, resin hardener and optical adhesive. Before boarding on an airplane with such substances, check if they are allowed in your luggage; otherwise, you will hopefully be able to find them where you are working. The aim of the APT Petro-Lab is to produce 1 millimetre thick sections, which will be then finished and cover slipped (if necessary) in the quiet of your laboratory.

Remember, safety first: always wear a laboratory coat, safety glasses, mask and nitrile gloves!

If you want to know more or if you have further suggestions for improving this kit feel free to get in touch.

Disclaimer: I assembled the kit under the guidance of my advisor Dr Patrick Sean Quinn, and my Supervisors Dr Cameron Andrew Petrie and Professor Charles Andrew French. The initial idea of a portable kit was inspired by the works of Chandler (2001) and Goren (2014).

References:

Chandler, G. M. (2001). Development of a Field Petrographic Analysis System and its Application to the Study of Socioeconomic Interaction Networks of the Early Harappan Northwestern Indus Valley of Pakistan. Graham Mansfield Chandler. Oxford: BAR International Series.

Goren, Y. (2014). The operation of a portable petrographic thin-section laboratory for field studies. New York Microscopical Society Newsletter, 2014(September), 1-17.