Alginate is a popular powder for molding, given that it is nontoxic and biodegradable, making it perfect for your more sensitive projects, like creating casts of your baby's feet or hands. As with most projects, it usually pays to think ahead so that you don't waste time or supplies with a lot of do-overs.

Planning Ahead

First, no two alginate casting projects are the same, which is why there are a lot of different powders and kits available. Do some research on powders to find the formula that has the right consistency and drying time for your project.

Once you've chosen your powder or your kit, buy more than you think you'll need. If you use too little, the objects that you're casting might poke through, creating holes in your mold, so it pays to be generous with your mixture. Also, this means that you will have enough powder to make a test batch, which we recommend you do. Before you commit to your final project, make sure you are doing it right.

Gathering Supplies

Your basic supplies will be your powder, water, a mixing bucket, and a mixing implement. The bucket must be large enough to hold everything comfortably with a little extra room in case the formula slops while you're mixing it. Your water needs to be the right temperature, which will be determined by the kit instructions. If it's too cold, the mixture will take longer to set, and vice versa. When you measure the powder, remember the ratios are measured by weight not by cups. These lead to very different mixtures.

Mixing the Powder

Put the alginate molding powder in the bucket first, not the other way around, or your mixture will get lumpy. Then you can add about 90 percent of your water and mix this for about half of the normal mixing time. Then you can add the rest of the water and stir it for the rest of the time. Remember that you should never mix it by hand. For anything under a pound, you can use a kitchen whisker, but for anything more than that, you will need either a Jiffy mixer or an electric drill.