Introduction: Casting a Pencil Holder
This Instructable will teach you how to create, cut, tape and cast a Pencil holder. Enjoy!
1x A large sheet of High Impact Polystyrene (Minimum of around 45x65 cm)
1x Pair of scissors or cutter (per preference)
1x Set square
1x Safe cutting ruler
1x Roll of tape
1x Fine line marker
2x Yoghurt cups of water
3x Yoghurt cups of plaster powder
1x Roll of tape
1x Bucket and Spatula
Step 1: Marking and Cutting Your Faces (mold)
In this step you will draw and cut the large sheet of High Impact Polysterene to create the faces which will in the next two steps will be taped to form your mold and core. To begin with draw the following on the sheet of HIP. Use a ruler and set square and start at the edge of the sheet to be space efficient. Using a fine pen (which gives off a thin line instead of a thick one) draw and label :
1x Rectangle - *13x8 cm
2x Rectangles - 13x10 cm
2x Rectangles - 8x10 cm
Once these are drawn and labeled take either the scissors or cutter (your choice) and cut the pieces. You should have 5 rectangles. Place the rectangles in a net, so that if they were to be folded they would create a rectangular prism (photo 2).
*Base x height
Step 2: Step 2: Marking and Cutting the Faces (core)
In this step you will draw and cut the large sheet of High Impact Polysterene to create the faces which will in the next two steps will be taped to form your mold and core. To begin with draw the following on the sheet of HIP. Use a ruler and set square and start at the edge of the sheet to be space efficient. Using a fine pen (which gives off a thin line instead of a thick one) draw and label on the remaining sheet of HI:
2x Triangle with lengths 11x11x8 cm
2x Rectangles - 11x5 cm
Label the the new shapes that were just drawn. Now just like previously in step 1, take either a pair of scissors or cutters and cut the pieces that were just drawn. It is highly recommended to draw the shapes next to each other, so that you can save the plastic.
Lay out the triangles and rectangles so you can form a triangular pyramid net (Image 3).
Step 3: Step 3: Tape the Mold
Next after you have layed out the 5 rectangles which form the mold, use a roll of tape, to tape the to form a rectangular prism. Make sure that the tape is on the outside and that there are no gapes in between the rectangles. This part is quite straightforward just make sure that you have covered the corners. To do that simply take a piece of tape and follow the images 2 through 4.
After you have taped it, you can try and pour water to make sure that none comes out. This will ensure that the plaster. will not leak.
Step 4: Step 4: Tape the Core
Same as the previous step you are to tape the two triangles and two rectangles that are to form the core. This time try to put more tape on the inside of the core and less on the outside (some will still be necessary). Remember to tape the corners and perform the water test (see below). To tape the corners you can go back and visit the previous step to learn how. It is also important that the tape on the outside does not have any air bubbles or wrinkles in it, as these will cause a hard time when sanding and pouring. After you've taped the core put a line about 3/4 up the triangle on one side (7 centimeters) that runs parallel to the top of the triangle.
After you have taped it, you can try and pour water to make sure that none comes out. This will ensure that the plaster will not leak.
At the end of this you should have 1 mold and 1 core, which should look somewhat similar to the third image.
Step 5: Step 5: Cast the Mold and Core
In this step, you will be creating the mixture that you will then pour into mold and core. Essentially, you will be casting your mold and core. The first step is to find a bucket and a spatula. Next pour 3 full yoghurt cups of water into the bucket. It is important that you have your mold and core on a table that can get messy. This is essential as once the mixture is poured, it will set quite fast and its important to quickly pour the mixture into your mold and core. After you have the 3 full yoghurt cups of water into the bucket, pour 4 and a half full yoghurt cups of plaster powder into the bucket. Now with the spatula, mix the powder and the water together. Mix until there are no small particles and the mixture is relatively homogenous.
Now (you will probably want a friend to help) set the core on a table that can get dirty. Take the mixture and pour it into your mold**. Then place the core into the mold and watch how much it displaces. You should push the core down until the mixture reaches the line. Then center the core so that it is in the middle of the mold and then hold it there for 2 to 3 minutes. Then, once the mixture has somewhat set, take a piece of tape and tape the core stuck onto the mold. Make sure that the core does not move in this process.
Now, wait around 60 minutes or until the plastic holding the pencil holder is no longer warm. (To be safe I waited a whole day.)
**This is quite confusing, as you will probably not need all of the mixture. I recommend to pour about 3/4 of the mixture and later, after you place your core, you can quickly remove the core and pour more.
Step 6: Step 6: Unmolding and Sanding
In this step you will have already cast a pencil holder. In this step get a cutter and slowly cut away the edges of the mold. Make sure that your cast is already solid. After carefully cutting the edges peal them away as in the first photo. Next to get the core out, I recommend that you try and wiggle the core out first. If this does not work, then you can just crush the core inside.
Once you have a pencil holder that is without a mold or core you will have to sand it. Get a sanding board and slide the pencil holder back and forth on all sides (be sure not to oversand as it could make a hole or make the hole in the mold to shallow which would means that the pencils would fall out). To sand the inside and get rid of tape marks, use a piece of sand paper. Sand the corners and edges so that you have a smooth sanded pencil holder.
Step 7: Enjoy!
Congratulations! You have now made a creative pencil holder. Enjoy your product and have a good time!