Hidden Worlds made Visible

The Archaeological Soil Micromorphology Meeting

Poviglio, Italy

May 27-29th 2009

Technician

•A person who is skilled in specific industrialtechniques.

• Somebody employed to do practical work ina laboratory.

• Somebody who has skills but lacks

originality or flair.

Craftsman

• Somebody who makes decorative or

practical objects skilfully by hand.

• Somebody who does something with great

skill and expertise.

Thin-sectioner

• Somebody who is employed to do practical work

in a laboratory, but is also trained in specific

industrial techniques, and can make decorative,

practical objects with great skill and expertise by

hand.

Over the last twenty years, I have learned that

•As a group we are shy.

•There are still more men than women.

•Most ‘sectioners’ are from the Earth Sciences.

•We all have very different laboratories, different equipment,different research needs and agendas.

•We all have our ‘trade secrets’. As in art, our secrets are ourhallmark, our ‘intellectual property’.

•In a career, an archaeological sectioner may produce around5000 slides - a geological/hard rock sectioner will produce nearto 10,000 slides.

We have all lost and won battles in

the desire to put

‘understanding to glass’

Each poster image in the exhibition has a

public description, and a scientific description

for the professional practitioners in the field.

The title of the scientific micromorphology

description is italised, unless the contributor

chose to combine the two methodological

approaches. The public is invited to read both.

Peruvian Agricultural Terrace Deposits. Dr Melissa Goodman Elgar, Department

of Anthropology, University of Washington, USA.

Andean farmers built stone terraces in the highlands of Peru to facilitate crop

production in their steep landscapes. Topography and harsh weathering make

terrace soils highly variable from terrace to terrace. This subsoil has weathered

rock and a very high clay concentration. Clay absorbs water in the wet season

which is released as soils dry out. This helps crops dependent on rainfall to

grow during the dry season. Cycles of wetting and drying contribute to the

spectacular colors of this slide.

Paca 1, 5F, 1995. Terrace Subsoil, Paca Valley, Peru.

The microstructure is blocky, platy in well-developed peds. The composition is

roughly 50:50 coarse rounded pebbles to fine material. The b-fabric is bright

mosaic-speckled, red to yellow clay in an open, single-double porphyric related

distribution. Laminated textural pedofeatures dominate the fine material as both

in situ and reoriented domains indicating vertisol properties. Porosity is low and

root is rare suggesting that this horizon limits root depth.

Original glass thin-section size: 75mm x 50 mm x 1mm.

What we do is difficult - there are still

unresolved problems

FIELDWORK: BE PRACTICAL - BE PREPARED.

• Carry a ‘Geoarchaeology toolbox’ of equipment and supplies suitablefor any location.

• Be strategic in considering the amount and size of samples needed.

• Sampling for micromorphology can be accomplished with thetraditional tins, but also with plastic sealable boxes, small cardboardboxes, foil boxes, waxed juice and milk boxes, tissue (paper towels)and tape, cling film and tape, sealed plastic bags, plaster, and ‘matchboxes’.

• STAY AWAY FROM: excessive wrapping, excessive use of clingfilm, plastic lined juice and milk boxes, and brittle plastics.

• TAKE THE TIME TO PACK SAMPLES SAFELY FORTRANSPORT.

What we do is difficult - there are still

unresolved problems

DRYING - TAKE THE TIME TO CONSIDER AIR DRYING ORACETONE REPLACEMENT.

• Judging from the soil or sediment content, which protocol would doless damage to the matrices of your samples.

• BE DISCIPLINED. Once a ‘drying protocol’ has been started, eitherby air or acetone, constant monitoring of the samples must occur toinsure quality.

• Record ‘drying artifacts’ in your samples. Be able to trace themthrough to your finished thin-section.

• STAY AWAY FROM FREEZE-DRYING, AND COMPLICATEDAND HAZARDOUS CHEMICAL PROTOCOLS.

What we do is difficult - there are still

unresolved problems

IMPREGNATION:

• Consider which type of resin to use, and how you would mix yourresin and chemicals to achieve ‘maximum infiltration’ of yoursamples.

• DON’T BE LAZY. Calculate your mixes for different soil andsediment types and monitor your results.

• The amount of vacuum pressure used (12 - 22 Hg), and the length ofthe vacuum period is dependant on the soil and sediment type, and thevolume/size of the samples.

• Check to make sure your resin and chemicals are within their ‘activeshelf life’.

• THE QUALITY OF YOUR FINISHED THIN-SECTIONS ISDEPENDENT ON THE QUALITY AND THE TIME PUT INTOGOOD IMPREGNATION PRACTICE.

What we do is difficult - there are still

unresolved problems

THIN-SECTIONING:

• ONCE YOU START - FOLLOW THROUGH. More damage is doneto a thin-section by delaying or abandoning the process half-waythrough.

• BE PATIENT AND USE OBSERVATION. After running a fewinitial slides, you should have the ‘feel’ of your material. Your samplesare ‘unique’, and should be treated with the respect and time.

• It is rare that the ‘perfect thin-section’ comes off the machine. Beprepared to ‘hand-finish’ to achieve a quality result.

• YOU ARE THE BEST JUDGE of the quality of your final thin-sections.

• TAKE CARE OF YOUR MACHINERY AND EQUIPMENT.

The main source of my business is ‘handling the

difficult and unresolved problems’.

My research over the next three years is to try and

refine and update the methodologies used in the

field, and in the laboratory.

With Thanks,

julie@earthslides.com, www.earthslides.com