Nov 3, 2019

Cheap Dice Molds Using Silicone Caulk

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A cheaper alternative to expensive pourable silicone mold kits. Best for amateur dice makers or resin casters who want a cheaper way to make molds for crafting. This is an inexpensive way to become familiar with the mold making process without wasting costly materials, however it does have some drawbacks, so if you are making dice for resale, it is a good idea to use the quality commercially available product to get the best results.
== Things You'll Need ==
*[[Image:IMG_4944.jpg|center]]
*silicone caulk--make sure to get Silicone I or a silicone that releases acetic acid during cure
*caulk gun
*paint thinner or mineral spirits
*cornstarch
*disposable measuring cups
*paintbrushes
*petroleum jelly
*hot glue gun
*dice or other items you wish to make a mold of
*six-sided pipped dice to form sprue (one per mold)
*mixing tool
*disposable paper or plastic cups
*razor knife or xacto
*paint to color the mold (optional)
*eyedropper (optional)
== Steps ==
#[[Image:IMG_4946.jpg|center]] Use a tiny amount of hot glue to attach one of the masters to the dice that will form your sprue. The best way to do this is to put the hot glue on a vertex of one of the masters, and to then line that master up with either the "one" or the middle pip on the "five" side of your pipped sprue dice. This makes sure your master comes into the least contact with the sprue dice and that it will be centered over the sprue.
# At this point, you will want to mix up your "mold release" which will prevent the silicone from sticking to your masters if they are finely detailed or if they have scratches. To do this, mix a small amount of petroleum jelly with a few drops of solvent (paint thinner or other mineral spirits). This is where an eyedropper comes in handy, but you can also eyeball this step. You want the mixture to be viscous enough to stick to the dice, but not so thick that it leaves brush marks when painted onto the master. To test this, mix with a paintbrush and run the paintbrush up the side of the cup. If, after a few seconds, you can no longer see the brush marks, but the material is still sticking the side of the cup, you have reached the right consistency.
# [[Image:Painting Mold Release.jpg|center]]Paint your mold release mixture on the faces closest to the sprue dice, which will be difficult to reach once you secure the master in the mold frame. Dabbing motions work best, to thoroughly coat without leaving brush marks. Try to make your application as evenly as possible.
# Next, glue the sprue dice to the bottom of a paper cup. For dice, I like to use a dixie cup size, but paper or plastic shot glasses will also work well. You want to leave enough room around your master that nothing will leak when you go to pour your casting resin, but not so much room that the thickness of silicone will be difficult to cure. If you are making a mold of something with a flat bottom, it is possible to just glue the object directly to the bottom of the cup, but for dice, a sprue is necessary unless you want a blank face. At this point, paint mold release onto the remaining exposed faces of the master die.[[Image:IMG_4947.jpg|center]]
# **BEFORE BEGINNING THE NEXT STEPS, MAKE SURE YOU HAVE ALL NECESSARY MATERIALS READY** The next few steps move quickly, so be sure to have everything open and arranged neatly. The ratio I have found works best is a 1:2 silicone to solvent ratio. It is best to work in small batches rather than making one large batch to distribute among multiple molds. This is because once the cornstarch is added to the mixture, the pot life is reduced significantly and you have less time to work with your material.[[Image:Silicone ratio.jpg|center]]
# For this tutorial, we will be using a 1:2 ratio of silicone to solvent. This creates a material that will be easy to pour but will still set in a reasonable time. Using a 1oz disposable measuring cup, one part (1oz) silicone to 2 parts (2oz) paint thinner or mineral spirit solvent will make almost exactly enough to fill a single dixie cup dice mold. Add your materials to a larger paper or plastic cup and mix until thoroughly blended and the texture is thin but not runny. If you would like to color your molds, add 3-4 drops of acrylic paint at this point and mix to combine. Before proceeding, grasp the cup and slam it down or drop firmly but carefully to bring any bubbles to the surface.[[Image:BEFORE MIXING.jpg|center]]
# This is the point where the process needs to begin to move quickly. Add cornstarch--for the above 1:2oz ratio, 2 teaspoons of cornstarch will yield a firm but pliable mold. Measure the cornstarch into the cup and begin mixing. Work quickly but carefully to avoid introducing too much air into the mixture. If the cornstarch is clumpy, try to "crush" the particles by stirring while pressing your mixing tool to the outer side of the cup. Some lumps are okay, but you want them to be fairly small.[[Image:Add cornstarch.jpg|center]]
# Using an old paintbrush, dab some of the mixture onto your mold, being careful not to disturb the mold release. A thin coat will ensure that no air bubbles come into contact with your master to create unwanted bumps on the surface of your mold.[[Image:Silicone paint.jpg|center]]
# Pour your silicone mixture into the cup with the master. To avoid trapping air bubbles against the faces of your master, pour into the empty space at the edges of the mold frame and allow the cup to fill up naturally. When you've reached the top or run out of material, tap the cup a few times on the counter or workbench to even the surface and dislodge any large air bubbles. Allow to cure for 1 hour or until the molds feel firm to the touch.[[Image:Pouring mold.jpg|center]]
# When your molds feel firm and no longer sticky, remove them from the cups. For paper cups, it is easy just to peel them away from the silicone by splitting the cup at the side seam.[[Image:Demolding.jpg|center]]
# At this point, I like to remove my sprue dice from the mold to allow more of the internal structure to be exposed to the air. Use your fingers to pull the silicone away from the edges of the die until you are able to get it free. To ensure even more air flow, cut slits into opposite sides of the sprue area and then about halfway down the master using a razor knife. If your master seems like it may come loose easily, you can remove it at this stage as well. If it still seems stuck, allow the mold to cure for another hour or so before attempting again.[[Image:Cuttingedge.jpg|center]]
# If at this stage, your master does not seem to be coming loose, you can use some gentle pulling at the sprue edge of the mold to try and coax it out. If anything begins to rip or seems like it may tear, stop immediately. You can try letting your mold vent for a while longer, or place it in the freezer for an hour or two to get the silicone to shrink away from the master. Be sure not to let your mold come into direct contact with any food items as it is still venting fumes--the acetic acid from the silicone is just vinegar, but the solvent fumes shouldn't be ingested.
# Allow your finished molds to cure for a few days until they no longer feel moist when touched. If you use the molds before this point, the venting solvent will inhibit the curing of your resin and you won't end up with pretty dice!! A good way to speed up this process is to place the curing molds in front of a fan with the sprue facing the fan to allow air to better penetrate the mold.
==Warnings==
*Since the main material of this mold is dissolved in a volatile solvent, most of which will evaporate off during the curing process, these molds will shrink as they cure. If your pourable silicone is well mixed, this should be a fairly even process, so you will get the same product once cast, just a bit smaller. This is one of the drawbacks of using a cheaper alternative to the high end commercial silicones. If this doesn't bother you, or if you are just using this method for personal enjoyment or to get a feel for the process, then this tutorial will work well for you.[[Image:Shrinkage.jpg|center]]
*If you do end up putting your molds in the freezer to shrink them away from your masters, be sure to do it AFTER your molds have set up and are firm to the touch, as freezing will denature any uncured silicone, which will not cure.
*Make sure during every step of this process to have proper ventilation. If you cannot open a window or door, wear a respirator. Depending on your solvent, wearing a respirator may be advised even with proper ventilation. Fumes released during the curing process and from working with solvents should not be inhaled for long periods.
*Certain fonts and dice styles will be trademarked--don't sell dice you've made from masters of unknown origin or you may face legal action.
==Tips==
*Use dice that are older or that you don't mind getting scratched--opening the molds sometimes requires cutting close to the dice with a razor knife which may scratch your dice.
*Also use paintbrushes that you don't mind losing, or ones you designate for this process. Sometimes the silicone mixture can be peeled away from smooth surfaces, allowing those items to be reused, but it is best to use tools designated for this to minimize waste. Do not use utensils or vessels used during this process to store or consume food.
*Use paper plates, plastic bags, or another work surface you don't mind getting dirty. Again, the silicone should peel off of most surfaces, but it's better to be safe than sorry.
*Typically I use the end of the paintbrush I use to paint the silicone onto the dice as my mixing tool, to save on waste, but popsicle sticks, a designated butter knife or spoon, and plastic silverware also work well.
*If you end up with a buildup of silicone on your work surface or mixing implement, let it cure and cut the excess away with a razor knife. The outside of molds can also be pared down or shaped using this method.
*This silicone will bond to itself, so if you find yourself running out of material before your mold is full, it is perfectly fine to mix up another batch and add it to the top either before or after the first layer has cured.


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