There are different types of epoxy resins available. This page gives a short overview of how to handle only one specific type, that is very runny epoxy resin (almost "like water") with a very long curing time (~24h), that will NOT interact with ("glue together") any other type of plastic material. It cures by mixing 2 products. (I don't want to advertise any products, so I will not publicly name them).
TL;DR: epoxy resin is only a mess to handle, if you don't handle it correctly!
Disclaimer: follow this tutorial at your own risk. Read data sheet and saftey instructions by your supplier carefully!
My first time fiddling around with epoxy resin was in November/December 2019 and I decided to go big right away. Because why not. After a few smaller trial run projects to get acquainted with the material (covering sea shells in resin, making key chains for the xHain advent calendar) I got started working on the large XHAIN epoxy resin letters. They were completed within a tight schedule, since they had to be finished in time for the 36c3 in Leipzig. I had been warned by friends that epoxy resin is an annoying mess to deal with, but luckily I was stubborn enough to ignore their warnings.
Many people continue to be interested in these letters, as they're displayed at the xHain-assembly during congress or in the xHain shop-windows, so I decided to finally write up a (lengthy and detailed) tutorial.
Object dimensions: 8x8x35cm, approx. 2.3kg
- The first image shows the finished result, with cloudy transparency due to use of too much dye. Also the heat disfigured the container (sheets of plastic), which created a wavy shape.
- On the second picture it can be seen how the wood (toothpicks) leaks air during curing, which creates bubbles in the resin.
- The third image (front and side views) depicts the bubbles, the poured layers of resin, as well as the cracks, which were created by too much heat and thus a fast curing process, which caused tension in the material. The cracks are only barely visible, thanks to the next layer filling up the gaps. To avoid heat and cracks, in this case the poured layers should not have exceeded ~1cm thickness. The cracked layer was between 2-3cm thick.
The very milky layer was due to using too much glow-in-the-dark powder. Unfortunately it was still not enough to create a visible effect, for the glow to show much more powder would have had to be used. This would reduce the transparency even further, which would not look nice.
So even though the glow doesn't show, the milky look, the bubbles and the cracks were not intended, the result still looks pretty. Depending on the project, you probably will want to avoid making these mistakes though.
Some stuff that went right or wrong during the making-of:
- X: looked fantastic during the making and was my favourite letter! But then things went wrong...
- I ruined the final result by accidentally adding too mucht pigment powder in the last couple of layers. The letter has turned so dark, that now all the tiny planets aren't really visible any more
- Also the transparent resin (solar system area) blended too much with the darker resin (outer space area with LEDs) and turned into a well blended, uniform mess. This was not intended.
- Some smaller areas stayed sticky and did not cure properly. This had to be fixed by covering them with another layer of resin. This worked out nicely though.
- The tiny (styrofoam) planets leaked some air. This looked horrible and was a mess to fix, but it can't really be seen anyway since the planets aren't visible
- H: this was the most problematic letter that never finished in time. Besides lots of holes and air-bubbles caused by the wood, there also turned up many large areas where the resin didn't cure. I'm not sure what went wrong, but probably I didn't stir the resin well enough since I was working under a lot of time pressure. Only hours before day 0 of 36c3 I was still scraping out sticky material and trying to fix it with new resin. The areas that I couldn't finish in time were covered up with spare sheets of overhead tranparency, so that curious fingers at 36c3 would not get stuck on the H. In early 2020 I took my time to properly fix all this. If you look closely, you can still make out the patched up areas.
- A: went as planned and even the jelly fish looks awesome
- I: didn't go as planned but looks great anyway. But not next to the blue A, so months later I replaced the blue "I" with a rainbow "I" instead.
- N: went as planned. It's the heaviest letter with >7kg. Contains no pigments/dyes, but lots of glitter and metals. And an octopus
Many months after the initial project:
- I_v2: rainbow version went as planned. I poured some more resin, lots of hearts and all my experience into this new letter.
- To avoid a blended dye disaster like I experienced with the letter X, this time I built a pouring-aid with precise dimensions. Quite some planning and calculations went into this, but it was well worth it: the result looks amazing!
- The layers were thick enough to turn warm during curing, which melted and bent some of the hot glue hearts, but I like it.
What you'll need:
- lots of patience!
- containers of epoxy resin A and B, in the ratio given by the supplier (in our case 2:1)
- throw-away (latex or nitril) gloves
- a bottle of <100% alcohol
- paper towels
- cling wrap
- plastic container for mixing product (e.g. cup of yoghurt, for large projects 1kg yoghurt "buckets" can be used)
- stick for stirring (e.g. toothpick or chop sticks for large volumes)
- kitchen scale (>100g) or letter scale (<100g)
- lighter (for busting bubbles)
- optional: coloured dye/pigments
- optional: deco objects, LEDs etc.
- for post processing: cutter knife, files or sand paper
- casting mould made of e.g. acrylic plates, laminated paper, paper covered with wide sellotape or similar smooth plastic surface material (3D-prints are not smooth! PLA also melts when resin gets hot!)
- sellotape, hot-melt gun and lots of hot glue
The curing process will create heat, which has to dissipate to the surroundings through its surface areas. If the surface-to-volume ratio is inappropriate, the heat will be contained within the resin and speed up the curing process. This can create temperatures of up to >100°C and can even melt through the container. The curing time, which is normally 12-24hrs, will shorten to ~1 hour. This will create tension and cracks in the material. Unless you want to use this as an artistic effect, it is usually not desired (and also dangerous) to let this happen.
Both during the handling and curing phase the resin will release toxic fumes. Do not breathe in and keep the room well ventilated!
Resin is toxic. Always wear gloves and do not let it touch your skin. Remove immediately with alcohol if this happens.
Read and respect safety notes of supplier!
- Most of your time, work and brain will be consumed by the brainstorming phase, the planning and preparation of the decorations.
- Wood, styrofoam and other hollow or "airy" materials will leak gas/air into the resin. Try to preprocess by completely covering with a thin layer of resin or transparent glue.
- Light object will float to the surface of the resin and also float about during the curing phase.
- As resin cures, it will shrink. Surfaces might end up concave. Consider filling up a little more to allow for shrinkage, or finish by covering with yet another layer of resin to reach the desired height.
- To estimate the total amount of resin you will need for your project:
- measure or calculate volume of your mould in cm³ (minus objects you put inside), Alternatively you can pour water into you mould and then weigh the water (this also checks for leaks in your mould).
- to measure the density of your resin: measure an amount of water in your mixing container (e.g. 300g) and mark level with permanent marker. Get rid of water. Fill your container with mixed epoxy resin up to this height. Measure resin. In our case 300g water = 321g resin.
- multiply volume in cm³ by weight of resin in g and divide by weight of water in g
- example: 8cm*8cm*35cm = 2240 cm³ = 2240/1000 ltr = 2.24 ltr = 2240g water = 2240g*321g/300g resin ~= 2.4kg resin
- Take your time to carefully read this entire tutorial before getting started!
First, brainstorm your ideas and buy all the matierials you will need. Research a little on the internet for inspiration, and don't forget to watch videos about "rivertables".... they are awesome
- Dyes: you can use food dyes (liquid), very fine powder pigments, or (expensive) pigments sold for epoxy resin by your supplier. Some (expensive) pigments have a beautiful pearly look, which have also been used in making the XHAIN-letters. Of course you can also mix in any type of glitter particles.
- Air leaking materials like dry wood or styrofoam are not beginner friendly. Try to avoid it for your first project, or be prepared to become frustrated. Before using it for a bigger project, figure out how the material is handled correctly by making a small trial run.
Images: Moulds made of laminated paper and silicon moulds. Click on the following image for a close up on the sealed edges (sellotape and hot glue):
These instructions only work with epoxy resins that will not connect with plastic materials!
- You can use any plastic material with a flat surface incl. hot glue. Silicone also works fine. For larger projects don't use anything that melts easily at <100°C (like cling wrap or PLA).
For a mould you can use anything made of plastic with a very smooth surface. For the XHAIN-letters I used old overhead transparency sheets that I had lying around. When I ran out I laminated A4 and A3 paper and cut it into my desired shapes. For small pieces like jewellery or key chains you can also use wide sellotape on paper and build various shapes out of that. For a keychain hole you can use plastic straws or roll a piece of paper and seal it with sellotape.
Any edges of tape will be visible on the resulting cast! (Put tape on outer side of mould.)
Basically (almost) anything that is not made of smooth plastic will stick to the cast and will not be removable!
Large moulds can be supported by sticking cardboard (use hot glue) on the outsides to give some stability.
3D-prints: due to the rough surface structure, 3d-prints are not ideal to use and are probably difficult to remove from the cast. You could try to smoothen the surface by sanding and polishing it (I never tried this). Also PLA will melt if you run into a heat problem.
You can connect the pieces with flat(!) sellotape, make sure there are no creases or the resin will leak through. If you leak resin, it will be a big mess and also your cast may be ruined.
Cover any edges very well with a thick layer of hot glue. Don't be economical!
- If in doubt, test your mould with water: does it leak? Fix it! (Dry well before use.)
- Also read step 10 carefully to see what else is important to consider when sealing the mould.
Plan to take your time. Do not work with deadlines! Expect a lot more to go wrong than you'd think!
- Remember that light objects will float to the surface. Think of a way to stick them to the place you want them to be. You can use invisible glue to stick to the mould or other objects, or you can pour a thin layer of resin in wich the light object will rest and be stuck to. Wait for the resin to cure (24h) before pouring the rest.
- Rember that materials that leak air, like dry wood or styrofoam, will have to be sealed with a layer of glue or ideally epoxy resin. Cover the object with a thin layer of resin and wait for it to cure (24h). Repeat the process to fill any gaps or holes (another 24h).
- Also painted objects might need to be sealed with resin, as the dye (like watercolours) may leak into the surrounding resin.
- Objects that are supposed to float in the middle of the cast will need to be supported somehow. You can either build a support structure with a thread for suspension. Alternatively you can pour the layer of epoxy resin first, wait for it to cure to the point where it is highly viscous, and then rest the object on top of it. Hint: Poured layers will be visible later on. To reduce this effect, do not wait for the full curation time, but only for the previous layer to cool down and become highly viscous first. Caution though: if you do not wait long enough you risk an overheating problem (and cracks in the material).
- For larger projects calculate or estimate the amount of resin you will need for your layer. A layer that is 1cm thick becomes warm and cures a little faster, but will not create an overheating problem and thus no cracks in the material.
- Smaller casts thicker than 1cm can be poured in one go, e.g. spheres or dodecahedron cubes with ~2cm diameter.
- Remember that the material will shrink during curing process. Be aware that you may need to pour a final thin layer at the very end to fill up any spaces, in case the precise height is important to you.
- Colours and dyes: You can use food dyes, pigment powders and glitter. Read section 4 for more details.
If cloudy streaks are visible then the resin needs to be stirred some more. Well blended resin shows no streaks (bubbles are acceptable).
Once you prepared your decorations and finished sealing the mould you can finally get started. Before mixing the resin, make sure to read the note at the end about pigment powders.
Make sure you ventilate the room well and do not breath in the toxic fumes released by the resin!
- put on gloves
- cover workbench with cling wrap (or plastic bag etc.) for protection.
- put kitchen paper towels and bottle of alcohol on your table. you will need it frequently for cleaning up leaks and messy bits.
- put mould on workbench
- put a layer of cling wrap loosely(!) on scale (any pressure or tension will mess with the measurements!). Use a kitchen scale for >100g or letter scale for <100g. Don't touch scale or cling wrap during measurement process. Make sure you use a scale that can measure fairly accurately and is appropriate for your volumes.
- put your empty/dry (yogurt) cup on the scale. Set a toothpick or chop stick aside for stirring.
- first do some calculations: for a mix ratio of 1:2 you divide your total amount by 3. Then take this number for the smaller bottle/container of resin (in our case product B) and double this number for the bigger bottle (product A).
- e.g. you want 90g of resin. 90g/3 = 30g. Use 30g of product B, 60g of product A.
- If your product requires a different mixing ratio, then follow your suppliers instructions instead.
- turn on the scale and reset it to zero. Now measure the components as accurately as possible.
- pour product B into the cup. If you accidentally poured a little more or less than you wanted e.g. 35g, then remember this measured number.
- reset scale to zero again.
- now pour the other product (A) by twice the amount of the previous measurement, i.e. 60g if you measured precisely or 2*35=70g to match the previous mistake.
- Hint: for the epoxy resin that I use, the component with the larger amount is more viscous than the other one and thus more difficult to measure. That's why I do it the other way round and measure the larger amount (A) first and use the smaller amount (B) later to compensate for any measurement mistakes I made. This is a matter of preference and practice.
- if you messed up the second round then remember the excess amount, reset your scale, and compensate with the other product again. Depending on your precision skills this process may have to be repeated several times, and the cup will end up with more resin than you wanted ... (of course you could also use two separate cups, but this is less environment friendly and imprecise when dealing with tiny amounts, since there will always be leftovers in the cups).
- for larger amounts it is enough to be precise up to 1g. For ~20g total weight I use my more sensitive letter scale and I pay attention to the numbers after the decimal point. Larger amounts are more lenient towards mistakes and easier for beginners.
Important: begin stirring immediately!
Don't wait around. Especially large amounts of resin will begin curing inside your cup very quickly and produce excess heat (up to >100°C).
Important: be patient when stirring!
Make sure your stir reaaaaally well to avoid sticky areas later on! When held under bright light you should be able to see streaks inside the resin mixture. Blend well until streaks disappear completely. Make sure to scrape around the walls and bottom as well to make sure you don't miss anything.
- Impatience leads to a sticky result, which will ruin your project for good.
Note: bubbles are OK, cloudy streaks are not!
- For smaller amounts (e.g. 50g) the resin will stay runny for hours, so no need to hurry. For larger amounts (>200g) there's no need for haste, but you should at least pour parts of the total amount fairly quickly within 10mins or so, to avoid an overheating problem in your cup.
- If the resin creates a lot of fumes and warms up quickly, then you waited too long. If it's still runny then hurry up to pour it, otherwise the mixture will be rendered unusable quickly.
- Dyes, pigments and glitter: now you can add some colour. The powdered pigments that I use are extremely potent. For the XHAIN-letters I used the tip of a toothpick to pick up a small amount of powder. I only used approximately 1-3 tips for 300g of resin. Adding more will make the resin more cloudy and less transparent. For a total resin thickness of 8cm this becomes too "dark". For thinner projects you can use more powder of course. Remember that what you will at first see is not what you will get at the end: adding more dyed layers intensifies the colour and makes it more cloudy. It is easy to underestimate this effect.
- If you want to create a mostly homogeneous/uniform colour-effect throughout all the layers, I propose two options:
- Either you weigh both your resin and the pigment carefully that you are going to use for each layer. Weighing the pigment is difficult though, and even my letter scale can't handle this accurately enough due to the tiny amounts. So I measure the powder in numbers of "toothpicks".
- If you are sure to know exactly the total amount of resin you will need at the end, or if you don't care to have some leftovers, you can also do the following. Take the total amount of one of the two components, measure it and mix it with your desired amount of pigment powder, stir well. Then, take an empty plastic container with a lid, like a clean/dry bottle of juice, and pour your component into this container. You can then proceed to mix layer by layer with the other component as you move along your project. Make sure to store the container in a cool and dark place, shielded from uv-radiation. Disadvantage: if you miscalculate or make other mistakes, you may end up with more or less than you need at the end. You may need to mix up some more at the end and you will have to "guess" the correct amount of pigment to add.
- There is not much to say. Slowly pour your mixture into the mould and distribute it well.
- You can try to pour with a thin stream of resin to get rid of some bubbles, but in my experience that doesn't help much. We'll deal with the bubbles in the next step.
- Don't be messy with the resin and try not to get it everywhere. Carefully pay attention to your mould.
If you discover a leak, stop pouring immediately. The resin will completely and slowly flow through the tiniest cracks! It will NOT stop.
- Once you tidied everything up you can also take off your gloves.
- Now go get your lighter. Any air bubbles on the surface can be busted by quickly touching it with a flame. Make sure it's only a brief contact, so that you don't burn the resin or any other material.
- Wait a while and come back to check for more bubbles. If your resin is warm then you need to check regularly. If your resin is cold or you poured a thin layer, you can come back after an hour or so.
The pro solution is to put your project into a vacuum chamber to push out all the bubbles, if you have access to such a chamber. Honestly though, my projects are too big to fit into these small chambers, I kinda like the bubbles anyway, and it seems too complicated for busting bubbles.
- If your deco objects are continuously leaking too much air, then it's too late now and you haven't read the preparation section. Jump back to step 3.
Ventilate the room well! Cover the mould (e.g. with cling wrap) to protect against dust.
- The hard part is waiting. I recommend waiting at least 12 hours before pouring the next layer, wait 24 hours before removing the mould from the cast.
- To soften the transition between the layers, you can try to not let the previous layer fully cure, but wait for it to become highly viscous and cooled down. But be careful:
- This is difficult to time correctly. You need enough time to regularly check back every hour or so. For multiple layers this can easily eat up an entire weekend. (Working under time pressure I have once even set my alarm-clock to wake me up at night to finish the project in time!)
- If you pour the next layer too early, the heat will accumulate and become problematic.
- In the end the layer transitions will not disappear completely. I recommend to plan for longer curing times and simply accept the visibility of the layers.
- Repeat the last few steps for pouring multiple layers.
- For the last layer, remember that the material will shrink slightly.
- If you want an exact result you may want to overpour the mould and sand it down later.
- Alternatively you can let the last thick layer shrink down a little, and then pour the very last thin layer up to the exact height that you want. (I'm lazy and always go with this option.)
Feels like christmas: unpacking the cast
- Use a cutter knife or any other flat tool to carefully remove the mould fromt he cast. Make sure to not scratch the surface of your object. Acrylic plates will most likely have to be broken and removed in pieces. Flexible plastic sheets can be removed easily with bare fingers.
You will notice, that depending on how accurately you sealed the edges of the mould, the edges will not look so nice.
- If hot glue flowed into the cracks, then you now have a negative imprint of the glue onto your cast. Tough luck. Next time it will probably work out better.
- You're lucky if resin flowed into the cracks instead. Now you have some excess material at the edges that you can remove using a cutter knife or sanding paper.
- If you dislike perfect but sharp edges on your material, you can also sand it down or use a cutter knife.
Postprocessing for lazy people:
- If you discover a rough, non-glossy, dull looking area on your cast, like from your cutter knife, then you can fix this by mixing up a small amount of resin. Use a letter scale, a small plastic cup (e.g. sauce cup from the sushi place next door) and a toothpick to measure and mix the resin. Stir well.
- Now you will need a steady hand and a good eye: Use a toothpick to dab some droplets of resin onto the dull areas and spread it until it looks nice. Wait another 24h and you will find that now all the areas look glossy and pretty. Yay! \o/
Postprocessing for perfectionists:
- If you have high expectations for your surfaces you can take your time to sand them down and polish them carefully. Make sure to wear an appropriate mask to filter the tiny plastic particles from the air! Do not breathe them in! You can find instructions on the internet. The whole process is very tedious and time consuming, but creates stunning results!
Be proud and share your work with the world! Send us a picture at xhain rocket chat or over at mastodon! We're curious to find out more about your projects!
- Don't move or touch the cast during curing time. Simply wait! Else you're going to ruin the surface!
- Don't pour thicker layers to speed up the whole process. Your layer will overheat and the material will crack.
- If resin doesn't cure in all the places: the components mixture wasn't stirred well enough. Take your time when stirring! Fixing this later on is nearly impossible!
- Edges weren't sealed properly. Use more hot glue! Don't be economical! This is also hard to fix, since hot glue or sellotape will not stick on surfaces covered with wet resin.
Some questions I've been asked:
- Q: How long can the opened/unopened epoxy resin containers be stored?
- A: My recommendation: not too long. After 6 months my resin was still usable, but definitely aged and yellowed. Better only buy as much as you are going to use.
Left: paper sprayed with a layer of hair spray/clear coat and covered with epoxy resin. Middle: Still wet quickdry cast (sprayed with and without hair spray) and epoxy resin filling. Right: test pieces after 6 months on the balkony.
Left: quick dry cast of hand. Top right: cast of face with embedded quick dry cast. Bottom right: successful epoxy cast of hand.
With a quicky dry cast I created very detailed copies of my face and hand and filled them with epoxy resin. Because the material is rather expensive, I first made a few test samples of my finger tips. (Since my finger prints are clearly visible, I had to remove them from the images.) I had read online, that one can use clear coat or hair spray to remove the resin from the cast more easily. So I tested this in two ways:
- First, I sprayed paper with clear coat and hair spray and then covered it with a thin layer of resin. I wanted to test if I could remove the resin from the paper later on. In both cases: nope!
- The clear coat even reacted badly with the epoxy resin and turned ugly yellowish.
- Similarly I tested the quick dry cast: I covered one with clear coat and left the other blank. The epoxy resin was easily removed from both casts, but the clear coat again created an ugly yellow taint and took away some of the details of my fingerprints.
- Quick dry cast: as long as the material is still soaked with water, the cured resin can easily be removed from the cast. But the cast easily dried out along thin edges, such that the dry powder got stuck in the resin.
- Images: a (failed) cast of my face with embedded power from the quick dry cast along the edges, and a (successful) cast of my hand made of iridescent white resin.