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Lab 2: Artifact Analysis

Lab 2: Artifact Analysis contains the following:

  • Optical Microscopy
  • Methodology
  • Chemical spot tests
    • Laboratory safety
    • Testing methodologies
  • Lead (Pb) spot test
  • Lab 2: Artifact Analysis Lead (Pb) Worksheet

Optical Microscopy

The stereo microscope (figure 2) is designed differently from the standard compound or light microscope. It produces a three dimensional visualization of the object being examined. The stereo microscope is primarily used to carry out close work such as dissecting, circuit board inspection, and geological examination. The light source for this type of microscope is very important. Reflected light is used to illuminate the sample and the power of the microscope seldom exceeds 100X.

Figure 2. Nikon optical stereo microscope

Figure 2. Nikon optical stereo microscope

Methodology

The stereo microscope (figure 2) is designed differently from the standard compound or light microscope. It produces a three dimensional visualization of the object being examined. The stereo microscope is primarily used to carry out close work such as dissecting, circuit board inspection, and geological examination. The light source for this type of microscope is very important. Reflected light is used to illuminate the sample and the power of the microscope seldom exceeds 100X.

 

Lab 2: Artifact Analysis – Methodology:

Set the microscope in a comfortable position and turn on the reflected light illuminator. Place a piece of white filter paper on the stage plate. This allows for easy cleanup. Place your group’s artifact onto the stage plate. Turn the zoom dial to low power and bring the image into focus.

Adjust the eyepieces for the correct distance. Do this by bringing the eyepieces closer together or farther apart until a single field of view is observed. Now, set the adjustment rings on both eyepieces to the zero position.

Use the zoom control to set the highest magnification. Bring the image into focus with the focus control. It is best to center the image on some clear point of detail.

Change the objective lens down to the lowest magnification. The image could be slightly out of focus. Do not adjust the focus with the focus knob. Instead, adjust the focus for each eye separately using the eyepiece adjustment rings. The microscope is now “parfocal”. This means that as the microscope is zoomed from high to low magnification the image will stay in focus throughout the entire range. Each individual would have a different setting. The stereo microscope is now set up for comfortable, all-day use.

With the artifact in focus, information that the naked eye missed can now be recorded. This data can illuminate the morphology of temper, marks made by tools, and even the fingerprints of the potter.

Turn to the ‘Lab 1- Artifact Documentation’ worksheet (pages 12-13) and verify that the artifact ID and Group# numbers are correct.

Record any additional features on the artifact that become visible due to the increased magnification. Observe:

  • Textures
  • Inclusions
  • Surface treatments
  • Enhance your sketch and description

The stereo microscope will also be used to view chemical reactions in the ‘Chemical Spot Tests’ section.

Chemical Spot Tests: Laboratory Safety

Safety is paramount. The laboratory is a dangerous place and attention to detail must be your primary concern. The use of personal protective equipment (PPE) is mandatory.

  • Goggles/Safety Glasses
    • The eyes are perhaps the most fragile parts of the body. Eye protection is mandatory when doing the chemical spot test. Besides splashing chemicals in the eye, fumes, vapors, and gases may cause permanent damage to the eyes and mucus membranes. Make sure your goggles/safety glasses fit properly and don’t obstruct your view.
  • Gloves
    • The hands are the part of the body most likely to come into contact with chemicals. The proper type of glove is also important because some chemicals can cross the glove/skin barrier. NCPTT will provide the proper type of glove to each student.
  • Working with Acids
    • Always add acid to water
      • This is very important because the dilution action is exothermic—Heat is involved—and spattering may occur.
  • Labeling and Disposal of Waste
    • Proper labeling of all chemicals and by-products will insure the proper outcomes for tests.
    • Waste should be disposed of in proper containers and the student should follow the manufacturer’s MSDS guidelines.
  • Allergies and Medical Conditions
    • If any student has any allergies or medical conditions that preclude the successful completion of the chemical spot tests, please inform the instructors at NCPTT and your teacher. We will accommodate any reasonable request.

Testing Methodologies

Chemical spot tests are used for confirming the composition of a material. Spot tests are rarely done on unknowns. The scientist usually has some idea as to the composition of the object in question. As the name implies, spot testing requires very little of the material for testing. This makes this technique suitable for the fields of archaeology and conservation where keeping the object’s integrity is very important.

INCLUDE A SECTION HERE ON “DO NO HARM”

The equipment for chemical spot testing is simple. It includes glass wells (depressions), porcelain, or plastic. Other supplies include glass or plastic pipettes, glass vials, filter paper, forceps, and an approved chemical spot testing kit (figure 3). This kit includes many of the common reagents needed for a variety of spot tests

Figure 3. Supplies for Chemical Spot Testing

Figure 3. Supplies for Chemical Spot Testing

Each chemical spot test is different in its methodology, but the equipment needed is basically the same. Pottery and ceramics are composed of several common elements and compounds. Clay is the most common material used for creating vessels and material culture. It is abundant and easy to work with. Every culture throughout pre-history and history has used clay for tasks like cooking, shelter, and defense. Clay is composed of basically silica and aluminum oxides.

If one looks at the prehistoric pottery, it is evident that the clay vessels were utilitarian with some decorations. The vessels were made of local or regional clay and contained some form of temper—Material used as binding agents and to allow for expansion while during the firing process—and were usually not glazed. The historic vessels became pieces of art and contained colorful patters and motifs. In order to obtain bright colors, potters used chemicals like Cobalt (blue), Copper (green), and Iron (black). Lead was used extensively for glazing and as a binder. Today the global community is aware of the dangers of Lead and its affect on child development. Still, developing countries do not have the capital or infrastructure to rid themselves of Lead containers and pipes.

In this laboratory exercise, we will test for the presence of Lead (Pb). As with all scientific procedure, a clear systematic approach is best.

Lead (Pb) Spot Test:

  • Equipment:
    • Glass Well Plates
    • Plastic Pipettes
    • Stereo Microscope
    • Ventilation Hood
  • Reagents:
    • Glacial Acetic Acid – Corrosive, Toxic, and Flammable
    • Potassium Dichromate – Oxidizer, Corrosive
    • Distilled Water
  • Protection:
    • Gloves
    • Goggles/Safety Glasses
  • Procedure:
    • Scrape a few grains off of the artifact in one of the wells.
    • With a glass rod deposit one or two crystals of potassium dichromate in same well.
    • Cover the contents of the well with one drop of glacial acetic acid.
    • Let sample and reagents sit in the well for one minute.
    • Carefully place the well plate under the stereo microscope and focus on the well that contains the sample.
    • Using a clean plastic pipette, add one drop of distilled water to the well and observe.
    • When the potassium dichromate crystals dissolve in the glacial acetic acid, the materials turn slightly yellow. It is not until the distilled water is added that lead chromate forms and is precipitated out. This precipitate is a positive test for lead.
    • Record any and all results on the Lead (Pb) Worksheet.
    • Clean area when done and ask NCPTT instructor to check your work area.

Now use the Conservation Scientist for a Day Lab 2 Worksheet, available for download below.

[Download not found]

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