TWO PART MOLD MAKING by Mary Ann Stage

TWO PART MOLD MAKING
by Mary Ann Stage
(click on thumbnails for a larger image)

Two-Part Mold Instructions - Again there are other ways to make molds but, this is how I do it.

Supplies:

1. A 3-dimensional item to mold
2. A piece of 1/4" or 1/2" Foam Core Board depending on size of item
3. Masking tape
4. Glue
5. Small ruler
6. Permanent marker
7. X-ACTO or craft knife
8. Wood stirring or popsicle sticks
9. Rubber Bands
10. Sandpaper
11. Paper Towels
12. Small, flexible, plastic cups you can throw away
13. Liquid Silicone Rubber (I use One-To-One/Rapid Mold Making Rubber from Micro-Mark). There are other products you can use but, this is what I use.
14. 2-Part Casting Resin (from Micro-Mark)
15. Rubber to rubber mold release (from Micro-Mark)
16. Floral Clay
17. Flat surface to work on

LESSON 1:

For this lesson, I`m showing you how to make a two-piece mold of a 3-dimensional object. The first thing you need is an item to mold. I used a lathe to make a pedestal out of a piece of wood that I used for all the statues in my Museum Castle. I usually work on a large piece of plywood cause your work surface can get messy and a flat surface is good for keeping your work flat and putting your finished molded object onto so it will dry flat. I also keep plenty of paper towels handy for spills

Next, make a box about 1" or so larger than your item on all sides with foam core board. Tape it securely. When the box is complete, take the floral clay and work with it until it is about 3/4" to 1" thick and will fit into the bottom of the box filling it right to the sides. Smooth it as flat as you can. Position your item with the bottom of your item touching one side of the box edge. This will make an entrance to pour the resin later. Next, put some talcum powder onto your item and press it into the clay so that it goes into the clay half of the way. You can put a mark on your item showing a halfway point. Be sure to remove the clay from the bottom of your item on the one side. Push the clay gently towards the item making sure it is tight against the item. This will be half of your 2-part mold. On all four sides of the clay around your item, make an impression into the clay with the end of a pencil. These will form locking keys to make sure both parts of your molds will align properly. You’ll see how it works later.

Next, measure out equal parts of rubber silicone - part A and part B. I use the small plastic cups marking an A on one and B on the other. I also mark a line on the cups showing how much I pour into each cup. Next, pour both A and B cups into another bigger cup and mix thoroughly until the mixture is one solid color. Part A is usually a white color and B is usually blue so, you can see when they are completely mixed. This can take up to 3 minutes depending on how much you have used. You can use a brush to paint a thin layer of the rubber onto your item to make sure it goes into all the cracks and spaces. This is to insure there are no air bubbles. Then pour the rest of the mixture over your item and the clay until it is completely covered and about another inch or so higher. It helps if you mark a line 1" over your item, then you will know when to stop pouring. The set up time for the mold is 4 hours so now you can rest after you throw away your 3 cups and mixing sticks!

LESSON 2:

After the 4 hours carefully cut two corners of the box and pull one side of your box down and pull away two other sides until you can pull the whole piece (clay and rubber) out. This way you won’t have to make another box. You can use the same box for the second part. Try and keep your item in the silicone rubber part and pull off the clay part. You will then have your item in the silicone rubber and 4 hole impressions will be visible. Next, put the silicone rubber and your item back into the box and tape up the torn edges. Brush mold release on the rubber surfaces only and into the locking keys all around your item (anything that is blue). This will prevent the two mold halves from sticking together and ruining your mold. Mix more equal parts of silicone Part A and Part B together and pour it into the box again making sure to go about 1" over the top of the item. Then, let this cure for another 4 hours.

When 4 hours are up, break your box away from your mold and gently pry open the two parts. You can then take out your original item. You now have your two-part mold

LESSON 3:

Before you can pour resin into your mold, you have to put the two parts together, matching locking pieces, and secure them tightly with rubber bands. Stand the mold up so you can pour the resin into the opening you created by putting your item right on one side of your box.

Next, using new plastic cups marked A and B, pour equal amounts of the two part resin in each cup up to your marked lines. Pour both A and B cups into another larger cup and mix thoroughly until the resin is clear – usually about one minute. This resin starts to cure fast in 3 minutes so I usually stir the mixture for about one minute until I feel the cup getting slightly warm then pour it into my mold. Let is set for about 10 minutes in the mold until the resin you see in the opening turns white and feels hard to the touch. Take the rubber bands off and gently pull apart the two halves. The item will be somewhat flexible when you first take it out but it will firm up quickly. This is usually the time to trim any mistakes away. If needed you can sand your item when it is totally hardened then paint it. I use regular acrylic paints.

Using this same two-part molding procedure, I also made the tall pillars for my project.

Happy Molding!