Detailed Procedure for Gel Synthesis

 

Materials:

•1/4 oz packet of Knox Gelatin (1)

•Microwavable glass container (1)

•Water

•50 mL graduated cylinder (1)

•10 mL graduated cylinder (1)

•A container for the gel to develop in (1)

 

Recipe for Making Gel (instructor’s version):

•Obtain a glass container which can be heated in the microwave.

•Pour 1 cup * (approximately 236.6 mL) of water into the glass container, then empty a 1/4 oz packet of gelatin into the glass container.

•Stir the mixture to dissolve the clumps of Knox gelatin in the water for one minute.

•After one minute of stirring, place the mixture in the microwave.  Allow the mixture to heat until it boils (roughly one minute). Be careful not to use a shallow container because the solution will foam as it boils.  Heating the mixture, causes polymer chains to dissociate into monomers (i.e. heating the Knox powder-water mixture breaks down any long bonds created by the Knox powder with the water).

•Remove the mixture from the microwave, then (if necessary) stir the solution further in order to fully dissolve any remaining clumps of Knox powder into the heated water or remove any large bubbles created. 

•Place the glass container in the microwave one more time and heat till the solution boils once more.

•Pour the heated solution into a mold or container (If you are trying to make a lens from the gel material, a clear watch glass will suffice.).  Label the container with the amount of water used to make the solution so you can keep track of the solution's concentration.

•Place the mold into the refrigerator (Allow the ½ and ¼ cup solutions to sit in the refrigerator for at least one hour, and the 1 cup solution 1.5-2 hours.).  Careful!  Make sure that the surface on which the samples sit is level.  Otherwise your samples will be slightly tilted and your data based on Brewster's angle will be incorrect.  You may have to place a board in your refrigerator and use sheets of paper to level it before placing the samples in the refrigerator.

•If the gel is difficult to remove from the mold, immerse the mold in hot water for just enough time to loosen the gelatin from its mold. 

Be careful! 

1) Do not heat the mold for too long because the gel inside may lose its shape (especially in the case of making lenses, the curvature of the lens may be lost after heating the mold). 

2) Do not get water on the gel because doing so would change the gel’s water content.

 

*Note: In order to vary the water to gel ratio, try ¼ cup (approximately 59.1 mL) and ½ cup (approximately 118.3 mL) of water with the 1/4 oz packet of Knox gelatin.

 

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