HELP! — I Added Too Much Hardener In Resin

mixed too much hardener with resin
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 a hardener (part b). The chemicals don’t harden by themselves. 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.

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 flash 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 get rid of. (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.

Now, let’s look at how 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 by 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.

Unpublished Blog Posts of Resin Obsession, LLC © 2023 Resin Obsession, LLC

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6 thoughts on “HELP! — I Added Too Much Hardener In Resin

  1. PLEASE HELP ME!
    I was busy talking yesterday while pouring and at that time I didn’t notice my mistake. I had earlier poured the first layer into my mold. Everything with that was great BUT the next layer I used only part B and thought at the time I used both A and B. So I poured the ‘mix’ on top of first layer with no part B!! What can I do ? Dump the wet layer back into the cup see how much pours back and batch it with part B? Mix and report??? Darn I don’t want to lose all my work.
    Please let me know asap.
    Sincerely
    Marilynn

    1. Hi Marilynn, I’m afraid there isn’t a way to add part B to the part A and this point and mix it well. You’ll have to scrape out your Part A and start over.

  2. I’m having issues with the platinum 1:1 ratio. I have been measuring part a& b with silicone measure cups equally but I run out of part a and have about 2 inches left of part b. How is that? So my husband said to just pour them and measure the bottles to keep them even. But then I’m using a half more of the part b. What should I do?

  3. I customized a skateboard for my boyfriend and casted it in resin. This was the first time I’ve used two part resin instead of uv resin and I ended up adding too much hardener. Do you think this will affect my design? I used acrylic paint for the design and it was fully dry like over 48 hours dry. Do you think he’ll still be able to ride it if he wants?

  4. My project (9”W x 2”D) does not harden and is very sticky. I used Let’s Resin. It said to use 2:1 ratio but I found that after 3 days it did absolutely nothing. I then tried 1:1, then 1:1 plus a little extra hardener. Started to harden then, but still sticky. I tried mixing longer than five minutes. I tried using a blow dryer. I tried setting a heater fan set a few feet away at 77 degrees Fahrenheit. The humidity in my house is high (+45%). I’ve tried everything it feels like and I’m just throwing money away at this point.

    1. I’m sorry to hear you’re having such trouble with your project! Sticky or uncured resin is a common but frustrating problem. Let’s break down the possible causes and solutions so you can resolve this issue and save future projects.

      Possible Causes of Sticky Resin
      Improper Resin-to-Hardener Ratio:

      Many resin brands (like Let’s Resin) require precise measurement by volume or weight. Deviating from the recommended ratio (e.g., 2:1) or adding “extra” hardener can disrupt the chemical reaction, leading to incomplete curing. Even a small error can have a big impact.
      Incomplete Mixing:

      Insufficient or improper mixing can leave unmixed resin or hardener in your project. Even if you mix for 5 minutes, if the sides and bottom of the mixing container aren’t scraped thoroughly, some material might not combine.
      Environmental Factors:

      Resin cures best at 70–78°F (21–25°C) in a low-humidity environment (ideally below 50% humidity). High humidity (like your 45%+) can introduce moisture into the resin, causing curing issues or stickiness.
      Incorrect Product Usage:

      Let’s Resin has specific formulas for different uses (e.g., deep pour, casting, coating). Using a shallow-pour resin for a 2-inch deep project may prevent it from curing properly.
      Steps to Fix the Sticky Resin
      1. Assess the Project:
      If the resin is sticky but not entirely liquid, it may just need more curing time.
      If it’s tacky or gooey across the whole surface, you may need to remove and redo parts of it.
      2. Test Environmental Conditions:
      Ensure the room temperature is consistently 70–78°F and set up a dehumidifier to lower the humidity below 50%.
      Avoid direct airflow (like a fan), as it can cool the resin and disrupt curing.
      3. Fix the Surface Stickiness:
      For Slight Stickiness:
      Coat the sticky surface with a thin layer of fresh resin (correctly mixed and measured) to recoat and seal the project.
      For Very Sticky or Gooey Areas:
      If the surface is wet and gummy, try wiping it down with isopropyl alcohol (90%+) or acetone to remove uncured resin before applying a new layer.
      4. Remove and Restart (If Needed):
      If the resin didn’t cure at all (liquid or extremely gooey), you’ll need to remove it entirely:
      Use isopropyl alcohol or acetone to dissolve and wipe away the uncured resin.
      Sand down any remaining residue and start fresh with properly mixed resin.
      Tips to Avoid Sticky Resin in the Future
      Measure Precisely: Use a measuring cup with clear volume markings or a digital scale if weight is required. Stick strictly to the ratio recommended by the manufacturer (e.g., 2:1 for Let’s Resin).

      Mix Thoroughly:

      Stir slowly and scrape the sides and bottom of the container to ensure all resin and hardener are combined.
      Mix for at least 3–5 minutes (longer for larger batches) until the mixture is clear with no streaks.
      Choose the Right Resin for the Job:

      For a 2-inch deep pour, make sure you’re using a deep pour casting resin, not a surface coating resin.
      Control Humidity: High humidity can ruin curing. Use a dehumidifier in your workspace to maintain levels below 50%.

      Keep a Test Batch:

      Mix a small batch of resin in a disposable cup alongside your project. This helps you monitor curing progress without disturbing your main piece.

      With some adjustments, your next attempt should go much more smoothly. Let me know if you need further clarification or help troubleshooting!

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