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Shrinking a Casting using NOVOCS Silicone Solvent
Shrinking a model is a common request from users of mold making and casting materials. The challenge is to shrink a model uniformly and with a high degree of predictability. The procedure should also be repeatable. Overview; A user can shrink a silicone rubber mold 18% - 22% by mixing NOVOCS silicone solvent with the silicone.

 It is possible and extremely easy to reduce the size of an original without any special equipment. Comparison of original sized model measuring 3” (7.6 cm), a casting out of a mold reduced in size to yield a casting that is 2 3/8” (6 cm) and a casting out of a mold reduced to yield a casting that is 1.9” ( 4.8 cm).

1 - It is possible and extremely easy to reduce the size of an original without any special equipment. Comparison of original sized model measuring 3” (7.6 cm), a casting out of a mold reduced in size to yield a casting that is 2 3/8” (6 cm) and a casting out of a mold reduced to yield a casting that is 1.9” ( 4.8 cm).
 A decorative rosette will be used for this demonstration.

2 - A decorative rosette will be used for this demonstration.
 The rosette master model measures 3” (7.6 cm) in diameter.

3 - The rosette master model measures 3” (7.6 cm) in diameter.
 A small base is used to mount the model.

4 - A small base is used to mount the model.
 A hot glue gun is used to secure the rosette master to the base.

5 - A hot glue gun is used to secure the rosette master to the base.
 A plastic cup is cut and used to contain the liquid silicone.

6 - A plastic cup is cut and used to contain the liquid silicone.
 Mold Star®  16 will be used in this project because of its quick setup and demold times.

7 - Mold Star® 16 will be used in this project because of its quick setup and demold times.
 NOVOCS®  is a silicone solvent that does not contain VOC’s.

8 - NOVOCS® is a silicone solvent that does not contain VOC’s.
 Mold Star® Parts A and B are dispensed in equal amounts.

9 - Mold Star® Parts A and B are dispensed in equal amounts.
 2 parts of NOVOCS® are dispensed.

10 - 2 parts of NOVOCS® are dispensed.
 Proportions; 1A:1B:2 parts NOVOCS®

11 - Proportions; 1A:1B:2 parts NOVOCS®
 All components are mixed thoroughly for 3 minutes.

12 - All components are mixed thoroughly for 3 minutes.
 Viscosity of the mixture will be very low.

13 - Viscosity of the mixture will be very low.
 Silicone is poured over the model.

14 - Silicone is poured over the model.
 Silicone is allowed to cure for 2 hours.

15 - Silicone is allowed to cure for 2 hours.
 Plastic cup is removed from around the mold.

16 - Plastic cup is removed from around the mold.
 Rubber mold is carefully peeled away from the model.  Rubber is very weak at this point and has low tear strength.

17 - Rubber mold is carefully peeled away from the model. Rubber is very weak at this point and has low tear strength.
 Mold is allowed to shrink for up to 10 days.  Mold is ready for casting and will yield castings that at least 20% in size vs. the original.

18 - Mold is allowed to shrink for up to 10 days. Mold is ready for casting and will yield castings that at least 20% in size vs. the original.
 Comparison of original sized model measuring 3” (7.6 cm), a casting out of a mold reduced in size to yield a casting that is 2 3/8” (6 cm) and a casting out of a mold reduced to yield a casting that is 1.9” ( 4.8 cm).

19 - Comparison of original sized model measuring 3” (7.6 cm), a casting out of a mold reduced in size to yield a casting that is 2 3/8” (6 cm) and a casting out of a mold reduced to yield a casting that is 1.9” ( 4.8 cm).

                   
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