Polyester resin casting a bangle bracelet

Bangle bracelet with polyester resin


polyester resin casting

Why polyester resin?

I’ve been motivated recently to do some polyester resin casting tutorials.  In my opinion, the best place to use polyester casting resin is for a piece where you want to put a high polish on the final casting with a buffing wheel and buffing compound.  For this resin bracelet, I’m using a plastic bangle bracelet mold and testing out a silicone ring mold.  (I always try out all our resin molds before including them for sale in the Resin Obsession store.)  For the inclusions, I’m using dollar store ‘Legos’.

By the way, if you are new to polyester resin casting, please read my post on 5 things you need to know before using polyester casting resin before trying this yourself.

What you do not see in this polyester resin bracelet tutorial is me having to talk my peeps that no true Legos were harmed.  Trust me when I say it was harder than the casting.

measuring depth of plastic resin mold

measuring depth of silicone ring mold

Measure the mold

When working with polyester resin, you have to begin with the end in mind.  For my castings, I measured the depth of the molds to determine the amount of hardener I needed to use.  (This is not something you need to do when using epoxy or polyurethane resin to make jewelry.)  The plastic mold measures 5/8 inches deep, while the silicone mold measures 3/4 inches deep.  According to the manufacturer’s instructions, I must add 5 to 6 drops of catalyst per ounce of resin.

What you don’t see here is that I am casting this resin outside.  Casting polyester resin in my studio was not an option this week, and because I hate the smell, it had to go outside.  Currently, the temperature outside in Florida is in the mid 90’s with fairly high humidity.  The ideal temperature for casting this resin is in the low 70’s.  Because the temperature is so warm, I knew I did not need that much hardener, but in the name of resin experiments, I decided to do it anyway.

I would regret that decision sooner rather than later.

fitting toy pieces into mold

Knowing I would not have much time to work once I mixed the resin, I wanted to be certain the block pieces would fit into my mold.  This means making sure they stay below the edge of the mold in addition to being able to fit into the curve of the mold.  Once I was sure pieces would fit, I prepped both molds with a light mist of Petrolease non silicone mold release.


measuring polyester resin

Measure and mix the resin

For this casting, I measured 2 1/2 ounces of polyester casting resin.  I knew two ounces would fill the bracelet mold, leaving me an additional 1/2 ounce for the ring.  For this amount of resin, I added 12 drops of catalyst and mixed for approximately two minutes.


pouring resin into the bottom of a plastic mold

Regardless of the resin you use, pour a little bit into the bottom of your mold before adding inclusions.  This will make trapping bubbles in your pieces less likely.

mixing lego pieces in resin

Before adding the toy pieces to the mold, I mixed them in my cup of resin.  This breaks the surface tension on the pieces to reduce the amount of bubbles that transfer into the mold cavity.

placing pieces into resin mold

Place the toy pieces

I used a stir stix to place toy pieces into the mold.  What you can’t see here is that my resin started to gel in under four minutes.   While the right amount of hardener was added to the resin-based upon my measurements, the outdoor temperature put the resin into overdrive.  (The manufacturer instructions state I should have 15 to 20 minutes to work with the resin before it starts to gel.)  It was a mad dash to shove pieces into both molds.  By the end, I was scooping jelly from my cup.

If you have ever had resin get too hot too quickly, this explains why resin gets hot.

resin gelling in cup


And for those of you wondering how I cleaned up the cup and stir stix?  I didn’t — I threw it all away.

Next, I covered the pieces and let them cure outside.  The smell persists for awhile.

lego piece resin bracelet


This is my finished bracelet.  (Upside was the pour side, which is the side exposed to air during curing.)  Overall, I’m surprised by how it turned out.  Putting gelled resin in the mold to fill it up had me concerned about demarcation lines.  Luckily, that didn’t happen.

Of course that doesn’t mean there aren’t some other problems I feel compelled to point out to you.  (like this is police interrogation or something similar)

resin bracelet casting

Casting results

A few of my toy pieces rose up beyond the edge of the mold.  I knew this as I was putting the resin in, but didn’t try taking them out once I realized everything was gelling so fast as that would introduce bubbles.

I know, you must be thinking, ‘Well didn’t you put pieces in the mold before you started this?’  How did this happen?  I didn’t anticipate how much the pieces would float in the resin.

sharp edge on resin bracelet

There are also sharp edges on this resin bracelet that need sanding.  That isn’t necessarily unusual as the resin will rise up along the edge of the mold while curing.  Unfortunately, though, I cannot sand the bracelet like I usually do because toy pieces are sticking out of the resin.  If you have never done this before, this explains how to sand resin smooth.

I will sand the edges so they aren’t sharp, but the top of the casting won’t be flat.  No big deal as the bracelet will be wearable and it is for me anyway.

The only other thing to mention is that the bracelet casting side (side exposed to air) was slightly tacky, but not as tacky as I was expecting.  I am hoping it will continue to harden over the next couple of days.  Since I can’t sand off that surface, I will need to use a layer of resin gloss sealer spray to get rid of the tackiness.

ring made with polyester resin

So how did the ring turn out?

In case you didn’t believe me about the resin getting hotter sooner than expected, this ring serves as proof.  The inside of the silicone mold used for this casting is perfectly smooth, which should have transferred to the ring’s surface.  Instead, the resin got hot and created a spider web-like cracking to the surface of the resin.

The resin is fully cured and the ring is sturdy.  Unfortunately though, coating with a layer of the gloss sealer spray will not get rid of the marks.  I could try sanding, but I’m worried I would sand down the toy piece or would need to sand too much off the ring shank to where it would break.  If I was serious about trying to salvage this ring, I would recoat it with another layer of resin.

Feeling the need to redeem myself, let’s call this polyester resin casting Part 1.  You can see how I improved things in this article:  resin casting a bangle bracelet

Unpublished Blog Posts of Resin Obsession, LLC © 2019 Resin Obsession, LLC

Like this post? You may be interested in  How to make your own Sea Glass

13 thoughts on “Polyester resin casting a bangle bracelet

  1. I’ve learned the hard way that if I’m mixing one big pot for several projects that the projects all have to be similar size to do the hardener correctly. One set of beads ended up so brittle 🙁 they ended up cracking! Ah well. Live and learn. So comforting to see I’m not the only one lol

  2. I’ve pretty much decided never to use the stuff. The challenges in using other resins are plenty without needing to add more problems! Thanks for taking this decision away from me! Big lol!

  3. Hello, and thank you for all your sharing! I wonder if you know about Polyurethane resin, and if there are some differences between Polyester and Polyurethane resin and working with them.
    Best regards

  4. Hi I have been using this resin as it’s much cheaper than epoxy to buy in the U.K. However the sticky layer on the air dried side is driving me crazy. Can I get rid of it completely or would I need to varnish? Thank you

  5. Hi recently I use clear epoxy raisin but hear was a problem after dray, that the result as like malted and flowing bubbles in the model see result in image and please briefer me if you have any tips to solution.

  6. Hello
    I’m from Portugal and I’m a beginner.
    I started with the Polyester resin … and I did not know nathing about resins 🙁

    What I learned is …
    – She smells VERY bad. I wear a mask and fans to give me air.
    – My resin takes about 1 hour to start getting hard / gelatinous.
    – She eats plastic cups … so I use paper cups (small coffee cups)
    – I can only use 1% hardener … and counting the drops was VERY complicated. So I bought a “mini” precision scale (like that of the gold and silver sellers). So I weigh the resin and then I put 1% of its weight … super easy and reliable, without errors.
    – She ate the COLORS of my natural flowers: – (… everything was white and the resin turned yellow.
    – I can make small quantities, for rings, bracelets, pendants … without problems of hardness or cooking.
    – I can do fine things … but it takes more time to stay very hard (about 2 days, depending of temperature of air).
    – Easy to polish (I use fine sandpaper), it stay super bright and transparent.
    – It create always a sticky layer on the surface.
    – In Portugal, my polyester resin .. 1 liter costs 15 € (euros) …. 1 liter of Epoxy resin, costs 36 € (euros).
    – The resin is very hard after it dries … but it breaks easily if it hits hard things.
    – I use oil-based pigments to give a transparent color, i use a very concentrated ink (1 drop gives 2 cups of coffee) … Attention, in Portugal the coffee cups are small 😉

    I learned a lot with your tips, it’s a spectacular site.

    Thank you

  7. Hello. I am from the Philippines, and I am a beginner for resins although i’ve crafted somehow. Thing is, epoxy resin is a hard access material here and it is very expensive. Only polyester resin is available in our local store, and many tutorials suggested beginners should start with epoxy resin but im stuck with this fiberglass. before I start my project, I need help from expects how to measure the catalyst; how drops every ounce ounce? considering also that its hot and dry here in the country. Mindanao on June has an average high temperature of 30 degree C, and i do not know how that temperature would affect the curing of the resin since most video tutorials I watched is western. I hope to find answers here in this blog. thank you so much.

  8. I had made some resin bracelets..with mostly fabrics inside..My problem is that they are all the same interior dimension 6.5 cms. They will fit over some hands but probably 60/70 % they will not fit..I wrack my brains ..Can I convert to use as something else or how do I sand the interior to make them larger..?..This is an 86 year old whose hobby is making but not in resin..They are really beautiful but they sit in my workroom to be admired nut unfortunately not worn..

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