Crystal Painting

Patricia Ann Riley             Lincoln Park High School
                               2001 N. Orchard Street Mall
                               Chicago IL 60614
                               (312)534-8130

Objectives:

 Students in grades 6 through 12 are to:
1.  observe a variety of naturally occurring crystalline solids;
2.  observe a variety of crystalline solids available in the supermarket, 
    drug store, or hardware store;
3.  use watercolor techniques, wax crayons, and the saturated solutions of the 
    crystalline solids in objective 2 to paint a picture;
4.  compare, write a description, and draw diagrams of the various crystals;
5.  exhibit the completed paintings.

Materials Needed:

Demonstration set:  Variety of naturally occurring crystals, such as quartz, 
    fluorite, citrine, amethyst

Per team of 4 students:
Crystal samples:              Saturated solutions (Tempera paint added):
CuSO4.5H2O (Root Killer E)    CuSO4.5H2O (Naturally blue; no paint added)
AlK(SO4)2 (Alum)              AlK(SO4)2 (Yellow) 
NaCl (Table Salt)             NaCl (Green)
MgSO4.7H2O (Epsom Salts)      MgSO4.7H2O (Red)

Per team of 4 students:    
wax crayons       newspaper       magnifying glass/microscope              
distilled water   paint brushes   81/2" x 11" white construction paper 
name labels       paper towels    large sheets black construction paper
small jars        tape            hot plates/hair blowers (optional)


Strategy:

1.  Advance preparation:  Make a saturated solution of each sample crystalline 
    solid (Root Killer E, Alum, Table Salt, Epsom Salts), using distilled water.  
    Be sure some undissolved solid remains at the bottom of each container; this 
    guarantees saturation.  Add a small amount of powdered tempera paint to each 
    saturated solution, except the Root Killer E which is naturally blue in 
    color.  Divide the paint solutions among enough jars for one set per team.
2.  Pass around samples of naturally occurring crystals.  Discuss what crystals 
    are, what they look like, where they are found, what they are used for, how 
    they are made.  Have the students note the color, shape, size of the 
    crystals.  Have them compare and contrast.
3.  Explain to the students that they are now going to use a variety of 
    crystalline solids used in their homes to paint a picture.  Demonstrate that 
    they first draw a crayon picture which they will fill in with a variety of 
    tempera paints dissolved in saturated solutions of the solids.  Stress that 
    they should use a different brush for each color of paint.  Emphasize that 
    the students are to stir the paint solutions each time they use them.  This 
    will insure that seed crystals will be mixed with the paint.  Also point out 
    to the students that they want to leave paint puddles on the paper.
4.  Divide the students into teams of four and give each student a sheet of 
    white construction paper.  When they finish their painting, they can either 
    let it air dry overnight or use a hot plate or hairblower; air drying is 
    better since slow evaporation produces larger crystals.
5.  Now have the students examine with a magnifying glass samples of the 
    crystals provided at each station.  They should consider shape, color, size. 
    They should write a sentence describing each sample's crystal and draw a 
    larger-than-life diagram of each. 
6.  Have the students examine their dry painting with a magnifying glass, write 
    sentences describing the crystals that have formed, and again draw diagrams.
7.  Discuss what the students observed.  Have them compare and contrast the two 
    sets of crystals:  the reference set at their station and the crystals in 
    their painting.  What happened to the crayons?  Why were the crayons used? 
    How were these crystals formed?  What effect did the paint have on the 
    crystals?  How might the students extend the lab?  
8.  Have the students mount their paintings on a sheet of black construction 
    paper with tape and affix a name label under the painting.  Display the 
    paintings as at an art exhibit.
9.  Have the students write a paragraph summarizing what they observed and 
    learned.  This and their descriptions will serve as a lab report.
    
Performance Assessment:
    
    Students will be assessed on completing and displaying their painting and on 
    submitting a lab report, consisting of a sentence description and diagram 
    for each reference crystal and each crystal in the painting and a paragraph 
    summarizing their observations and conclusions.  This will count as a full 
    lab grade.  Content of the painting itself will not be graded.  The teacher 
    should monitor the work in progress to insure that gang signs and other 
    unsuitable content are not used, but should not otherwise censor the work.  
                                  
    Students will also be assessed on the material on the next test.

Conclusions:

1.  Different substances produce different crystals.  The crystals of a 
    particular substance will have a fixed shape and color; their size depends 
    upon the amount of time allowed for growth.  This means that substances can 
    be identified by their crystals.
2.  One way to form crystals is through the evaporation of a saturated solution.
3.  The paint does not alter the crystal shape or color.  It did coat the 
    outside of the crystals and act as a glue to help the crystals stick to the 
    paper.
4.  All of the solids used in the painting dissolve in water and therefore will 
    not normally be found in nature.  Naturally occurring crystals do not 
    dissolve in water and must be formed by a different method.  One possible 
    method would be crystals forming as a molten liquid cools.  This would 
    happen in places such as volcanoes and lava flows.