How much resin should I mix?
When it comes to making things with resin, one of the tricky parts is knowing how much mixed resin you’re going to need. It’s important to make sure you have enough, but of course, you don’t want to waste any when making your resin jewelry and crafts. Here are a few tips and formulas to help you figure out how much resin you’re going to need for a project.
1. The most straightforward way to figure out the amount of resin you’re going to need is to pour water into your mold, then measure that volume of water. A few key (approximate) measurements are:
1 milliliter (mL) equals 1 cc (cubic centimeter)
1 teaspoon equals 5 mL
1 ounce equals 30 mL
Know that you are not going to catch every drop of water as it comes out of the mold, so you will have to adjustment your measurement upwards a bit.
When doing this method, you will need to make sure your mold is dry first before pouring in the resin.
2. The second way of figuring out how much resin you’re going to need is going to involve a little more math. You can take measurements of the mold cavity and figure out the volume.
Here’s an example: A cavity is 1 inch square by 1/2 inch deep.
1 inch x 1 inch x 1/2 inch equals 0.5 cubic inches. 1 cubic inch equals 16.3871 milliliters Therefore, this mold cavity will hold approximately 8.189355 mL (the math is 16.3871 x .5). I would just round up to 9 mL here.
What do you do if it’s a cylinder or a sphere?
Cylinder volume equals Pi (which is 3.14) x radius2 x height
Sphere volume equals 4/3 x Pi (which is 3.14) x radius3
Note: Radius is the distance halfway across. Diameter is the distance all the way across. To get radius, you will need to divide the diameter by 2. Don’t even ask me where that Pi number came from.
So here’s an example that I use quite frequently. I’m going to make a casting with bangle bracelet mold 414. Here are the dimensions: 2 5/8 inches inner diameter, 5/8 inches wide, 3/4 inches tall.
Let’s get the volume of the ‘outer’ circle: 2 5/8 inches plus 5/8 inches times two (two because of each side) equals 3 7/8 inches total diameter. Using the formula above, the volume of a cylinder that size equals:
3.14 x (3.875/2)2x .75 which equals 8.84 cubic inches.
But hold on, we need to subtract the inner cylinder, otherwise, it’s like we’re filling up the entire bracelet without a hole for your wrist.
Inner cylinder volume equals:
3.14 x (2.625/2)2x .75 which equals 4.057 cubic inches.
That means the volume of the bangle is 8.84 cubic inches minus 4.057 cubic inches which equals 4.783 cubic inches. Using the standard above in point 1, 4.783 cubic inches equals 78.38 milliliters. Divide that number by 30 and you get approximately 2.6 ounces of resin needed for your project.
A couple of other things to keep in mind with this:
1. Resin needs a minimum amount of resin and hardener to generate enough heat to start the curing process. Make sure after you have made your calculations that you are mixing the manufacturer’s recommended minimum mixing amount.
2. Always err on the side of mixing a little more rather than a little less. If you have some leftover, have some backup projects ready to go. One of my favorites is turning your favorite scrapbooking papers into wearable jewelry using resin.
3. To make sure you get accurate measurements, I always recommend using graduated cups. We have them in the 1 ounce and 10 ounce size. The 1 ounce cups have milliliter marks on them as well as ounce marks.
Phew! Now that I’ve made your head spin, go cast some resin!