Wooden ruler
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When determining the value of a piece of jewelry, one of the most important factors is figuring out how much the item weighs. Unfortunately, most of us don't keep jewelry scales around our houses and household scales won't do the trick. Luckily, with a little ingenuity and understanding of some basic rules and facts of weight and balance, you can improvise a device for measuring the weight of your jewelry using household objects.

Lay the dowel on the table and secure it in place. Use a lump of stick tack and spread flat beneath the dowel, then press the dowel into it to stick it. Make sure the position of the dowel is relatively level with the top of table.

Place the ruler on the top of the dowel, positioned perpendicular to it. Use the dowel as a fulcrum on which to balance the ruler, like a see-saw.

Stick lumps of stick tack to both the bottom of the measuring cup and the top of the jar lid. Place the jar lid, overturned, on one side of the ruler and place the measuring cup on the other. Adjust the position of both objects, moving them closer to or further from the center, until you can balance the ruler again.

Put the jewelry you want to measure inside the overturned jar lid. Make sure the jewelry is gathered as close to the center of the lid as possible.

Gradually add water to the measuring glass until the ruler balances in mid-air again. If necessary, use measuring spoons and make a note of how much water you add.

Calculate the weight of the quantity of water you added. One cup of water weighs 236.59 grams, so divide this number by the fraction of a cup of water you needed to balance the makeshift scale. Thus, if you added a half a cup of water, the jewelry weighs 118.3 grams or 4.17 ounces.