Introduction: All-Purpose Paperweight
This Instructables will go through step-by-step how to build an all-purpose paperweight and pencil holder out of plaster.
- Cutter and/or scissor
- Scotch tape/cello-tape
- Sanding board
- Sand paper
- Plaster powder (2 cups)
- Tap water, room temperature (3 cups)
- Large polypropylene sheet
- Stirring tool
- Drill (5mm or 6mm drill bit)
- color dye(optional)
Step 1: Drawing the Net
Drawing the pentagons correctly can be a challenge. Therefore, it is important to refer to this video (credit to Arthur Geometry), if you do not already know how. Use a pencil and an eraser to facilitate the process in case any mistakes are made. Using a ruler, trace 3.5cm long lengths for the pentagon. Any smaller or bigger isn't favorable. Instead of drawing pentagon by pentagon, it is much quicker to simply draw one, cut it out, and then use it to trace the remaining pentagons. This will ensure that all pentagons are equal in size. The triangles, on the other hand, can be drawn individually if preferred. I would highly recommend you do so.
Step 2: Cutting Out the Net
Depending on the material you have chosen, use a cutter or a pair of scissors to cut out the net. Choosing to cut out the different parts individually or altogether is for you to decide. However, if you chose the cut them out individually, use the diagram above to help guide you.
Step 3: Taping the Polypropylene Parts Together
Begin by taping the pentagons together into what will look like a half-dodecahedron shape as shown in the images above. The pentagons should naturally bend in that direction making it easier to put together. Then, stick the triangles in the gaps between every pentagon. If one of the triangles is not to the right size or sticks out a bit, do not hesitate to trim it. It is hard to guarantee that the triangles will be the right size and therefore, this will most probably happen. Do NOT FORGET to leave a hole to pour the casting into. When taping, be very careful not to put any on the inside of the mold. Once the plaster hardens, the imprint left by the tape will be seen. Likewise, make sure to add multiple layers of tape. All corners and edges need to be firmly secured, otherwise, the plaster will leak through as it is being poured into the mold.
Step 4: Making Plaster and Pouring It Into the Mould
Grab a bucket and start by pouring in 3 cups of water. Then, combine 2 cups of plaster powder and slowly stir both components together. Use a spoon or any type of stirring tool available to you. While doing so, do not forget to wear an apron in order to avoid getting any mixture on yourself, and if you wish to feel safer, wear goggles. Adding color to your product is also an option. If so, 30 drops are more than enough, however, if you wish for a more radiant color then feel free to add more. Once it has been mixed, pour the mixture into the polypropylene mold. The plaster hardens in 10 to 20 minutes time, so don't take too long to pour it in. Make sure it is completely filled up and let it rest until the plaster has completely dried. If the plaster feels warm, do not take it out, it means it isn't completely ready yet.
Step 5: Removing the Mould
At this point, the plaster should've completely hardened and it is time to remove the mold. When tearing it off, be very delicate to avoid damaging it in any way. If the tape gets in the way, use a cutter to cut it off. Once the mold is removed, it can be thrown it away.
Step 6: Sanding the Casting
Using a sanding board, sand any uneven faces or corners of the product. As for smaller details, it is best to use sanding paper. It will ensure more precision. Always hold it very firmly when sanding and sand it in an up-and-down movement on the board.
Step 7: Drilling the Holes
On any 3 faces of the shape (preferably next to one another), drill a hole using a 6mm drill bit. It is important to make the holes big enough for a pencil to fit through. Do not drill all the way through it, stop at about halfway. If you do not drill the hole deep enough, the pencils will not be able to stand up straight and they will be sticking out too much. Remove any excess plaster left on the drill. If not, continuing to drill will be impossible as it will simply not rotate on its own.