At some point when you’re crafting, you might wonder what happens when you use too much hardener in resin. Or maybe you just realized you did, and you’re asking yourself if your resin will cure okay. There are a few things that could take place. But before we get to that, let’s discuss what resin is and why hardener is essential.
When using two-part resin kits, you’ll get a bottle of resin (part a) and hardener (part b). The chemicals don’t harden on their own. But, once you mix them together, the mixture heats up and solidifies in minutes to hours. Each kit has specific directions explaining how much of each to mix together to make this happen.
Now, you might be thinking that if a bit of hardener is good, a lot must be better to ensure your resin cures. So let me tell you why using too much hardener in resin is NOT a good idea.
Your resin’s pot time is reduced.
Pot time, also known as open time, is the time you have to use the mixed resin and hardener before it starts curing. When using too much hardener, the mixture heats up too quickly and may cure before you ever get a chance to use it.
Your resin may cure in a hardness you weren’t expecting.
Depending on the resin formula, your resin might cure harder than expected. But with other formulas, your resin may cure bendy and soft. Yep. It doesn’t make a lot of sense, but having too much hardener leads to curing problems.
You won’t finish both bottles at the same time.
Resin kits are meant for you to run out of both bottles of product at the same time. While it isn’t unusual to have a little bit left of one liquid, you don’t want to have a lot of Part A resin leftover that you have to dispose of properly. (You should never pour resin liquids down a drain or throw them away in your trash.)
So what do you do if you add too much hardener?
If you’re lucky enough to know immediately that you did it, don’t use that resin. Get it somewhere it won’t cause a fire as resin can get very hot and smoke. If you realize this later, it’s probably because something didn’t turn out as expected. In that case, let’s look at why you could have added too much hardener to the resin.
You measured by weight.
Carefully follow the resin kit’s directions for mixing. Many two-part resins measure by volume, not by weight. If you measure by weight, you will almost always use more hardener than is needed.
💡 Pro tip: If you use a scale to measure your resin and hardener, ask the manufacturer what the mixing ratio is if you measure by weight.
You wanted to speed up curing.
Yes, heat is good to speed up resin curing, but it should come from other sources that you can control. You can use a heating pad, small space heater, or a toaster oven dedicated to resin crafting to help speed the process along.
You didn’t read the directions.
Every resin kit has specific instructions that apply only to that kit. For example, you can’t assume that all resins mix together in a 1:1 ratio. If you use a resin that combines two parts resin to one part hardener but you mix one part of each, you will definitely use too much hardener.
You didn’t measure precisely enough.
Measuring inaccurately is one of the biggest mistakes I see in resin crafting, especially with beginners. It’s vital you use graduated mixing cups (cups that have measuring marks on them) to do your measuring.
Are you frustrated with making resin mistakes?
I’ve been there too. I remember how upset I was spending hours on a project only to have it cure sticky and full of bubbles. Then, I figured out that there were a few key things to know to ensure I made something I couldn’t wait to show off. I’ve detailed them all in my ebook, Resin Fundamentals. For less than the cost of a resin kit, you can go from confused to confident with resin in only an afternoon.
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