This is an accordion element with a series of buttons that open and close related content panels.
What is a crystal?
A crystal is a solid that consists of various atoms, ions, or molecules arranged in a uniform three-dimensional repeating pattern. This results in the material having a specific shape and color, and having other characteristic properties. Diamond (used in jewelry and cutting tools) is an example of a crystal. It is made of pure carbon. Salt and sugar are also examples of crystals.
Recrystallization is a process that has been used to purify solid material by dissolving the solid (called a solute) in an appropriate liquid (called a solvent) and then having the material precipitate out of solution in crystalline form. Depending upon conditions, one may obtain a mass of many small crystals or one large crystal.
Crystals are characterized by type, shape, form, clarity, and color.
What is the crystallization material and how can I get it?
Middle school students and home-schooled youths (ages 11-13/14) will grow crystals of alum, KAlSO4.12H2O (potassium aluminum sulfate, dodecahydrate).
High school students home-schooled youths (ages 14-18) will grow crystals of cupric sulfate pentahydrate CuSO4.5H2O.
Middle school teachers will grow crystals of potassium dihydrogen phosphate (KH2PO4; KDP).
High school teachers will grow crystals of potassium dihydrogen phosphate (KH2PO4; KDP).
Once you fill out the registration form the chemicals will be sent to the teacher’s address in February 2026.
How to grow crystals
The crystal growing period is from March 1 to April 30, 2026. The judging will take place on May 8, 2026 by a panel of judges.
RULE 1: The maximum amount of starting material that may be used for each given crystal is limited to 100 g.
RULE 2: So that all students have an equal preparation time, crystal production must conclude within six weeks after receipt of starting material.
The 2026 Handbook describes the crystallization procedures applicable to all three compounds.
How the Crystals Are Judged
Each school is encouraged to submit one crystal for best quality and one for best overall. It is recognized that several crystals from a school may be of roughly equivalent overall quality. If this is the case each school may submit several crystals.
Judging Criteria
One single crystal will be judged only on the basis of quality as outlined below. The other single crystal will be judged on the basis of combining mass and quality factors as outlined below.
The quality is judged by experts who will rank the crystals on a scale of 0 to 10. A score of 10 will be given to a perfect gem-quality crystal that fits the ideal crystal structure known for the chemical.
1. The crystal is weighed, and the mass Mo recorded. The crystal must be a minimum of 0.5 g to be eligible for judging.
2. The quality of the crystal is judged on a scale of 1 to 10, with 10 representing a perfect crystal.
The following factors will be considered in judging quality:
- match/mismatch with crystal type (out of 2)
- presence/absence of occlusions (out of 2)
- intact/broken edges (out of 2)
- well formed/misformed faces (out of 2)
- clarity/muddiness (out of 2)
Total Observed Quality Qo = x.xx (out of 10)
3. The Total Score is then determined as follows:
Total Score = [log (Mo+1)] x Qo
The logarithm of the mass is chosen so that large poor quality crystals don’t swamp out smaller good quality crystals. The value 1 is added to the mass so that crystals weighing less than 1 g get a positive score.
A 100 per cent yield crystal made from 100 g (Mt) that scores a perfect 10 on quality (Qt) would get a theoretical maximum of:
[log (100+1)] x 10 = 20.01
The actual score is expressed as a percentage of the maximum. The crystal with the highest Overall Score is the winning crystal.
100 x {[log (Mo+1)] x Qo} / {[log (Mt+1)] x Qt} = Overall Score %
For example, the best overall crystal in the 2001 contest with 150 g starting material weighed 46.53 g and had a quality of 8.65. Its overall score was:
100 x {[log (46.53+1)] x 8.65} / {[log (150+1)] x 10} = 66.6%
This score is nearly an absolute score that could be used to judge different types of crystals grown from differing amounts of starting material.
Safety
Potassium dihydrogen phosphate is safe but the usual safety precautions should be exercised. Gloves and goggles are recommended. The SigmaAlrdrich Safety Data Sheet for potassium dihydrogen phosphate provides exhaustive safety information.
Potassium aluminum sulfate, dodecahydrate is safe but the usual safety precautions should be exercised. Gloves and goggles are recommended. The SigmaAlrdrich Safety Data Sheet for potassium aluminum sulfate, dodecahydrate provides exhaustive safety information.
Cupric sulfate pentahydrate can be purchased from Flinn Scientific or Farm & Fleet. The SigmaAldrich Safety Data Sheet for cupric sulfate pentahydrate provides exhaustive safety information.
The crystallization materials for the competition are purchased from Flinn Scientific.