Introduction: How to Make Molds From Potatoes and Cast Concrete Rings (Jewelries)

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Since I already have experience with concrete, this time I decided to use concrete to make very unusual jewelries (rings). First of all I needed to make a mold for casting. I have already made molds from sand (https://www.instructables.com/Water-Lily-Planter-F...), boards and cardboard (https://www.instructables.com/Frame-Made-of-Yarn-a...), but making small molds for rings out of these materials wouldn't be so easy. So I was thinking how and from what I could make these molds. I didn't want to spend money and time making molds out of silicone or anything like that. And then I saw that there is a new contest for the use of potato (https://www.instructables.com/contest/potato/). As a result, I came up with the idea to use potatoes to make these molds.

  • Potato is fairly hard material and mold made of it will keep its shape,
  • you can cut anything out of potato,
  • potato is an organic material and the concrete should easily come off after hardening,
  • it's the most affordable and cheapest material.

This idea seemed to me just brilliant. Later I found out that people have been using potato molds to cast small things out of silver, such as bullets. But I did not find that someone used such molds for concrete casting. I was very curious if I could make molds out of potatoes and cast my planned concrete jewelries (rings). In this instructable I will tell/show you how I brought my idea to life. Also you will learn how to make miniature carving tools.

Supplies

    two potatoes (larger than the required size of the rings),

    a knife,

    wire (I used copper wire) 0.8 mm and 1.5 mm,

    a wire cutters,

    cement high quality,

    very finely sifted sand,

    water,

    semiprecious or any decorative stones - I used brown goldenstones,

    a container for mixing concrete,

    a tea spoon,

    a ruler,

    scissors,

    a felt-tip pen,

    a compass or a round object of the right size (I used coins),

    a piece of tin (from a tin can),

    scissors for metal,

    pliers,

    a board,

    a nail,

    a hammer,

    insulating tape,

    sandpaper,

    a toothpick,

    a disposable razor,

    primer, varnish for concrete.

    Step 1: Planning

    I decided to use several methods of casting and, accordingly, to make three types of the rings:

    • the Ring #1 with concrete head only, other parts of this ring will be made of wire (braided);
    • the Ring #2 will be completely made of concrete - cast in one part of mold;
    • the Ring #3 will be completely made of concrete with semiprecious stones on head (mold will consist two parts).

    Step 2: Making Wire Strip for the Ring #1

    You have to braid wire strip. Determinate the ring blank length:
    Ring blank length (mm) = inside diameter (mm) + 2 (thickness of the braided strip, mm) x 3.14

    Cut 3 pieces of 0.8 mm wire to the following length: Ring blank length (mm) x 3,18.

    Bend these pieces in half and insert the nail where the fold is and fix these wire pieces by nailing them to the board. You will have 6 pieces of wire with which you will braid.

    I offer you two ways for braiding: move the wire pieces along the edges one by one to the middle (see first and second photos) or like on third and fourth photos. Braid until you get the length you need. Using pliers press the wire strip. In the result you will get tight braided wire strip.

    Step 3: Making Wire Part of the Ring #1

    Using the felt-tip pen bend the wire strip in the form of a ring. Check if the resulting ring diameter matches the required. If it's necessary, unbraid it a bit.

    Now you have to connect the ends of the wire strip. Insert 4 wire pieces into the loop (where was the nail), tighten the ends of the wire and try on or check if the ring matches the required size. Bend the left wire pieces (on the sides) around the end of the wire strip. Twist all ends of the wires.

    Then you have to form a reinforcing support for the concrete head of the ring. Bend the ends of the wires to form something like a reinforcing mesh (see photo). This mesh must be a bit smaller than the planned concrete head of this ring.

    Step 4: Making Reinforcing Wires for the Rings #2 and #3

    Cut off two pieces of 1.5 mm wire to the following length: Ring blank length (mm) + 30 or 60 mm .

    Bend the wires neatly around the felt-tip pen to form rings of the desired diameter. Twist the edges.

    You will get two wire rings.

    Step 5: Prepare the Potatoes

    Take 2 potatoes of the needed size (larger than the required rings). The potatoes must not be rotten.

    Wash the potatoes.

    Cut the potatoes in half: one half of the potato for the ring # 1, the other half for the ring # 2, two halves of the second potato for the ring # 3.

    For two halves of the first potato, cut a little edges on the opposite sides of the cut already made so that the parts of potato will be not wobbly (see photo).

    Put the other two halves of the second potato together and cut the edge perpendicular to the cut already made (see photo).

    Place the pieces of potatoes in water.

    Step 6: Making Carving Tools

    To carve such small molds you need miniature carving tools.

    Making a Cutter for Narrow Strips

    Using scissors for metal, cut a narrow strip out of the tin (see photo).

    Bend the strip and form a loop on the end - in the middle of this tin strip (see photo). With this loop you will cut out the strips in potato. You can make loops of different widths to cut strips of different widths accordingly.

    Form the handle - insulate the opposite side (see photo).

    While carving, clean the cutting loop with a toothpick (see photo).

    Making a Miniature Scalpel

    Using pliers break off the sides of the disposable razor (see photo). Be very careful!

    Choose a suitable blade and using scissors for metal trim the edge - this will be the cutting part of this scalpel.

    Keep a plastic back part of the disposable razor and form the handle of this miniature scalpel - insulate the opposite side (see photo).

    Practice cutting with this tools on unnecessary potato pieces.

    Of course if you have the suitable carving tools, then you can skip this step and start carving - forming the mold.

    Step 7: Potato Carving

    Determine which pattern you want and can carve.

    Making the Mold for the Head of the Ring #1

    I decided to make the head of this rings round. Using miniature scalpel cut a circle (around the coin, for example).

    Using the cutter for narrow strips cut out the middle of the circle and carve pattern (see photo).

    I made two such molds with different pattern (see photos).

    Making the Mold for the Ring #2

    Using the miniature scalpel cut a circle again (around a coin whose diameter matches the size of the ring).

    Using the cutter for narrow strips cut out the strip around the circle - it will be a shank of this ring.

    Carve in the same way the head of this ring (see photo). The head will be narrow.

    Making the Mold for the Ring #3

    Take one half of the potato and carve the mold for the shank of this ring like for the ring #2.

    To make the head of this ring not narrow, carve deepening equal to half of the planned head.

    Determine how high the head will be, join the two potato halves and cut out the top.

    Carve in the second half of the potato the other half of the head (see photos).

    Step 8: Concrete Casting

    Prepare a concrete: mix 1 part cement and 1 part sand well, then add water and mix well.

    Casting the Concrete Part of the Ring #1

    Using the spoon pour some concrete in the mold. Stick the wire head of the ring into the concrete (see photo).

    Casting the Ring #2

    Pour some concrete in the mold. Then place the wire ring, made in the step into the mold. Pour more concrete (see photo).

    Casting the Ring #3

    Pour some concrete in the mold for the shank (the first half of the potato). Then place the wire ring, made in the step, into the mold. Pour more concrete. Cover with the another part of the mold (join the parts of the head) and fix it with wire (see photo).

    Pour concrete into the mold of the head and stick the semiprecious or decorative stones.

    Leave the concrete to harden and dry for several days.

    Step 9: Final Details

    Carefully cut molds and remove the rings. Sand the edges carefully, rinse. The concrete rings turned out really very unusual. I liked the rough texture of the concrete so I barely sand. Coat with a primer, varnish and leave the rings dry well. Enjoy the work done.

    Conclusions

    I prefer the rings with the concrete head and braided wire shank.

    The purpose of my instructable was to show the possibility of using potatoes for making molds for different casting methods.

    Of course, the quality of the cast will depend on how well you can carve the pattern. But if it's difficult for you, then you can simply put a piece of plastic with nice texture (or a piece of leaf, or flower) on the bottom of the mold made of potato. I am sure that you will always find a solution to the problem if you use your imagination.

    I would also advise you to grease inside of the molds with oil before pouring the concrete.

    Potato Speed Challenge

    Runner Up in the
    Potato Speed Challenge