How much resin should I mix for a project?
Originally published October 2014. Updated February 2019.
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, crafts and paintings. If you find yourself asking ‘How much resin do I need?’, here are a few tips and formulas to help you figure out how much resin you’re going to need to mix for a project.
If you are working with something with ‘sides’, like a mold or bezel, the most straightforward way to figure out the amount of resin you’re going to need is to pour water into the item, then measure that volume of water. A few key measurements are:
*1 milliliter (mL) equals 1 cc (cubic centimeter)
*1 teaspoon equals 5 mL
*1 ounce equals 30 mL
*1 cubic inch equals 16.3871 milliliters
Know that you are not going to catch every drop of water as it comes out of your mold or bezel, so you may want to mix a little more resin to account for this.
Make sure your item are dry first before pouring in the resin.
For the times when you want to be more exact, or if you are trying to calculate the amount of resin to go on a flat surface like a painting, you can take measurements of the area and figure out the volume of resin needed by multiplying the length times width times height.
Here’s an example: A mold cavity is 1 inch square by 1/2 inch deep.
1 inch x 1 inch x 1/2 inch equals 0.5 cubic inches. Since 1 cubic inch equals 16.3871 milliliters (from option 1), this mold cavity will hold approximately 8.189355 mL (the math is 16.3871 x .5). I would just round up to 9 mL from here.
Or, you can use this resin calculator
(If you you are trying to cover a painting, doming resins generally level to a depth of 1/8 inch, so use 0.125 inches as the depth)
This article explains more for calculating the amount of resin to cover a painting.
What do you do if you are casting resin into a cylinder or sphere?
We’re are getting deep into the math now. 🙂 Cylinder volume equals Pi (3.14) x radius2 x height. Sphere volume equals 4/3 x Pi (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.
Here’s an example I use quite frequently. I’m going to make a casting with with this chunky bangle bracelet mold. 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. Since 4.783 cubic inches equals 78.38 milliliters (4.783 x 16.3871), divide that number by 30 and you get approximately 2.6 ounces of resin needed for your project.
Other things you need to know if you are asking how much resin do I need:
1. Resin needs a minimum amount of resin and hardener mixed together 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. The flip side of that is true as well. Make sure the amount you need doesn’t go over the manufacturer’s maximum recommended mixing amount. If it does, you will need to divide that amount up into the appropriate number of castings so you don’t generate too much heat at once.
2. Always err on the side of mixing a little more rather than a little less. If you have some leftover resin, 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!
Unpublished Blog Posts of Resin Obsession, LLC © 2019 Resin Obsession, LLC