April 2017

# Stained glass spiral periodic table

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Mike Tomac (retired), Morro Bay High School, Morro Bay CA

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In 2015 my students and I finished a long-term, multiple month project making sort of a "stained glass" spiral periodic table. Our creation is now attached to the classroom window at Morro Bay High School. The glass tiles illustrate the first 19 elements from hydrogen to potassium. Initially we had set a lofty goal to have the 92 natural occurring elements. It became apparent that less would have to do — our small kiln could fit only one tile and each required 24 hours to heat. We found a spiral design and liked that it showed periodic trends. These glass tiles took about three months to make because we had to learn how to use the kiln and test out different heating schedules and types of glass. This was a class project done in small increments and spread out over one and a half semesters. It involved side experiments: testing different types of glass and their kiln schedules; methods to prevent devitrification (crystallization) of the glass which would result in foggy appearance; and testing various methods to color the glass.

Our enthusiastic crew of chemistry artists

At first we attempted to use recycled colored bottle glass, but the tiles that resulted were not crystal clear and too dark. So, instead, we used leaded glass and added a fine sprinkling of copper(II) oxide for green coloration and cobalt(II) oxide for cobalt blue color. This decision was based on practicality, effectiveness and cost. Through our side experiments, we found that the cobalt and copper compounds were very effective in making nicely colored glass. We had plenty of cobalt oxide and copper oxide in the chemical storeroom. We would have loved to include red colored glass but that would have required gold oxide. This explains why red glass is so rare.

After making a clay mold for each element, we placed them in plastic sandwich containers and poured #1 casting plaster (a standard and common heat resistant type of plaster) mixed with sand around the clay. The clay was then dug out, resulting in a plaster mold that can withstand kiln temperatures of 1500 °F. For each mold, we used a solid block of leaded glass. We received a donation of a few 5/8 inch thick leaded glass port holes (viewing windows) from a local artist who acquired them from U.C. Berkeley's radiation facilities. With a tile saw these were cut into blocks to fit into the rectangular cavity of each plaster mold. The oxides (copper or cobalt) were sprinkled on top. Each rectangular block of glass was then melted in the kiln to fill each mold's cavity.

For the background, we cut out 19 square holes in a half sheet of 3/4 inch cabinet grade plywood to hold each glass tile. Because Morro Bay High School is near a beach, a beach theme (sand and rope) was chosen. We thoroughly mixed two parts beach sand with 1 part white glue and troweled it onto the plywood to give it a spiral textured pattern. The glass tiles were securely attached in each hole with Glazier's Steel Push Points (steel nail-like fasteners).

After everything was done and the spiral periodic table was on display with sunlight shining through, it was fun to see the students walking by. They smile and point at the particular elements they were personally involved in making. What an adventure for them and me.

## The process in pictures of our stained glass spiral periodic table

The window with the sun coming in through tiles.

Spiral of stained glass tiles embedded in wood ready for installation.

Making a clay mold for each element.

Clay mold for helium.

Pouring casting-sand mix to make plaster mold.

Clay mold is used to make a plaster mold — ready for the high temperatures of the kiln

The leaded glass mixture in the plaster molds after the kiln

Glass tiles in their plaster molds.

Glass tiles removed from their plaster molds.

Glass tiles embedded in the wood, which is covered with a beach-sand glue mixture. The texture of the background and rope around each tile symbolize our beautiful beach. Notice the colors: green from copper(II) oxide and blue from cobalt(II) oxide.

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## More about April 2017

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  Activities Sorting the atomic model

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  Series Early submissions to New Elements Contest