Rijacki Design

Alchemist’s Workshop Basics: Epoxy Resin – Mixology

Ms_Rijacki1A tutorial on how to mix 2-part Epoxy resin.

When ever I work with epoxy resin, I feel a bit like a mad scientist in my alchemist’s workshop mixing up chemicals, cause I am. Muhahahaha, and I shall take over the world! err umm…

Alchemist’s Workshop is an on-going series of posts on working with resin, clay, and various other mixed media.

This blog post is intended to demystify the process of mixing up epoxy resin.  You should not feel intimidated by epoxy resin. It’s actually pretty easy to work with, once you know a bit about it.

Epoxy resin is generally two parts which need to be mixed before use. The ratio of the parts depends on the brand of the product. Once the two parts are mixed together, they begin a chemical reaction which makes the resin increasingly less liquid as time passes until becomes as hard as it will ever get. The process is called curing.While the curing process does generate heat in the reaction, it’s not heat that is making the cure occur, though you can speed up (or slow down) the cure with external temperature (i.e. very curing space can cause a faster cure while a cold one can slow it down).  Epoxy resin generally fully cures in 24-hours which is why it is sometimes called 24-hour resin.

TIP: Each time you open a new box of resin or a new resin “kit”, read the instructions that came with it. Look for the important bits as outlined below. Even if you’ve used that particular resin before, still at least glance at the instructions to make sure nothing has changed with their formulation.

1 to 1 resin is used in all the example images for this article.

Suggested Safeguards while working with epoxy resins:

  1. Avoid to resin on your skin. Wear non-porous gloves such as nitrile, vinyl, or latex.
  2. Avoid getting resin in your eyes. Wear goggles especially when sanding any resin pieces and even while pouring.
  3. Avoid breathing the resin fumes. Work with epoxy resin in areas of good ventilation and/or use a fan to keep the air moving. For other resins, such as polyester, you may need a respirator and to work outdoors exclusively.
  4. Avoid breathing resin particles. When sanding, wear at least a paper mask.
  5. Avoid getting resin on your clothes. Wear an apron. Resin on cloth cannot be cleaned off. It will permanently bond to the fibers even without curing.
  6. Read the instructions for the resin brand every time you open a new package of the resin.
  7. Read the MSDS (Material Safety Data Sheet) for the resin brand.

Minimum Equipment Needed to Mix Resin:

  1. 20150105_215341Two medicine cups: For easier  measuring of the 2 parts, use two medicine cups that have measurements on the sides (graduated cups). Many resin kits will include at least two of these cups or they can be obtained from a variety of sources, such as your local drug store. The cups you use with resin cannot be used for any other purpose. For best results with most of the 2-part resins, use 2 identical cups for measuring. While it is possible to get calibrated cups, you’re likely to use the measuring marks more as a guide than for precision.
  2. Stir sticks: You can use wooden popsicle sticks (most resin kits will include a few), small plastic paint spreaders (I found some pink ones at the Loonie/Dollar store, called paint or glue spreaders), or any other flat long ‘stick’  that will easily fit in the cup where you will be mixing the resin. Resin Obsession has some rather nice inexpensive plastic stir sticks: http://www.resinobsession.com/ItemPage/5394/ResinObsession-Stir-Stix-StirStix.html (white paddle-like stick in the picture). The advantage of a non-wood stir stick is a potential reduction in the number of bubbles introduced during the mixing phase.
  3. Timer: To ensure you mix the resin thoroughly, a timer can help a lot. While it is possible to do the “one mississippi” count, I consider a timer to be non-optional. A cheapie timer is probably best because you will get resin parts on it and really shouldn’t use it for any other purpose and especially not around food once you’ve had it around uncured resin. I got my digital timer at the Loonie store for a couple dollars. (Canadian dollar is called a Loonie because of the Loon on the coin. Thus a Loonie store is a Dollar store for those of you in the US, I just like the name better *impish grin*)

Suggested Equipment Needed to Mix Resin:

20150105_2151361. Protect your work area: Something to cover your work area to protect vs. possible spills or resin wet tools being laid down. Wax paper, kitchen parchment paper, or even a plastic grocery bag work well. I like the flatness of wax or parchment paper and the fact I can tear it off in smaller pieces as I want for mixing small bits of resin with pigment.

Tip: If the spot you will be leaving the items to cure is different from your pouring area, don’t forget to cover your curing area as well. If you’re using credit cards or other still card stock under an item so you can move it, cover it with wax paper (or which ever) as well. Over fill spills can really ruin your day if the item you’re making sticks to the surface where it was curing. (Yes, I do know this from experience.) For best results, the area you’re using to cure should be level. If it’s not level, the liquid in the resin will gather at one end of your project and possibly even spill over. At the least, it might make your resin project not have an even amount of resin across the item.

2. Protect your clothing: An apron to cover your clothing. I found a sailcloth one at the Loonie store for a couple dollars that works perfectly for me.

20150105_2238583. Protect your uncured resin: Covers for the curing resin to prevent unwanted additions to the resin (like dust, dander, hair, or anything else that could fall on it or be blown on to it). Covers can be anything as long as it’s high enough and wide enough to have absolutely no chance of touching any of your curing resin. It’s to prevent unwanted additions, not to become one. (and, yes, sadly, I had exactly that happen one time when I didn’t have ample room above a curing item and didn’t realise it slightly touched. I found a couple plant pot liners at the Loonie store which were 50 cents each and work superbly for most of my resin pouring. If items or molds I am pouring won’t fit under my pot liners, I’ll grab other things around me that have a high clearance. TIP: Clear covers allow you to visually check on the curing resin; opaque ones are the mystery spot.

4. Keep the resin level: If you’re pouring into a bezel with an integrated bail, you will want to elevate the bezel so the bail doesn’t put the bezel at an angle. You can use one or more coins, such as a quarter or twonie, in a stack under just the bezel leaving the bail to hang off the side. Use a small piece of wax paper (or whatever you’re using to cover your workspace) to go between the coins and bezel. You can also use a rack which won’t stick to the resin such as the one offered by Resin Obsession. Position the bezel so the bail is in an open area.

5. Aim for fewer bubbles: Something that can provide directed heat, preferably without a lot of wind such as an embossing tool, a blow dryer on low, a wand lighter (though I personally am a bit leery of the open flame around chemical fumes as well as just an open flame in general), or even just a drinking straw you can blow through. Directed heat can help reduce bubbles.

6. Clean up: Wet wipes are the greatest things since sliced bread. When you start going through them like new parents with a baby that has diarrhea, find a place you can get them in bulk. Nail polish remover and cloth you can throw away is also rather handy.

7. Finishing molded resin: After you demold resin items, you will generally need to do some finishing work to smooth edges. Sharp scissors and sand paper sheets in various “grits” and/or sand paper conveniently attached to a stick commonly called an Emory board or nail buffer (especially one of the multi-sided, multi-grit ones) are the items you should have on hand. The dollar store is a great source for the nail buffers and Emory boards.

Planning the Pour:

Planning ahead is important. It can be the difference between a successful project and one which fails to meet your expectations.

1. Decide how much resin you want to mix up.

  • Small batches are easiest to work with when you are starting out. Plan to make no less than 1/2 ounce of resin in a batch. If you make less, it might be harder to stir and might not combine correctly.
  • If you want to use the medicine cup for your mixing, you’ll also need to make sure your planned full amount of the 2 parts together is less than the maximum of the cup’s size with ample room for the liquid to move (i.e. be stirred) without sloshing over.
  • I usually aim for no more than 1.75 ounce of resin for a small batch in a 2 ounce medicine cup. You’d be surprised how many items that small amount of resin can make.

2. Doing the maths.

  • If you’re using a 1 to 1 ratio resin, the math is easy, each part will be 1/2 of the total amount.
  • If you’re using a 2 to 1 resin, one cup will need to be filled at exactly 1/2 of the amount of the other.
  • The instructions that came with the resin will tell you which ratio to use and, if it’s a 2 to 1, which one is the 2 and which is the 1.
  • Finally a use for that algebra from school *smirk*

3. Finding the mark.

  • Medicine cups are usually marked with several different measurement types: ounce, dram, ml, etc. It doesn’t really matter which of the measurement types you use just as long as you use the same measurement for both parts.
  • You can mark the outside of both of your cups at that point to help you see exactly where to stop when pouring the parts from their bottles.
  • You can also mark the cups A and B, to help you easily distinguish between them though, for most resins, there is a colour difference in the 2 parts when they’re inert and not mixed together.

I usually pour 3 drams of each part when I am using a 1 to 1 ratio resin. I just use the line on the cup. I should have marked my cups for the pictures but I’ve gotten so used to hitting -that- mark pouring less or more feels odd to me.

Preparation Before Mixing:

20150105_215059There are two major factors you should consider for your prep, what can I do to minimize bubbles and the limited time you will have once the resin is mixed (pot time, see below).

1. Bubble avoidance:

  • Since cold can develop more bubbles, warm up the resin parts in water bath, give it the resin spa treatment. Before you pour open the bottles to pour into the cups, dry the bottle off completely so you don’t accidentally drip water where you don’t want it (i.e. into the resin parts).
  • If you’ll be using molds, warm them up a bit, too, but with something other than water or anything else that can leave them moist (resin -hates- water, when it’s mixed in to the resin). If you have an embossing tool or blow dryer, you can blow it over the empty mold.

2. Planning and prepping what you want to do with the pour:

  • If you’re going to be using molds or bezels, have them close at hand and ready to go.
  • It’s actually best to have a few additional items ready just in case your planned items take up less of the resin than you think they will.
  • If you’re going to be using colourants or any other inclusion (item to go -in- or under the resin) make sure they’re fully prepped and close at hand as well.
  • Once the resin is mixed, with 2 part epoxy resin you generally only have 20-30 mins to do all the pouring you intend (with other resins that time is drastically shorter, so get into good habits with the much forgiving epoxy resin before you go to them).

I’ll go more in depth on various ways to prepare molds, inclusions, bezels, and other stuff to incorporate into resin in later posts. If I included them here, this would end up as an even longer novelette.

NOTE: One of the parts (generally the hardener or B) might appear slightly yellow in comparison to the other. Do not fear, if the resin label says that it’s clear, it will actually mix clear without that tint. It will clear up while you’re mixing in a magical chemical reaction.

Pot Time:

latestPot time is the amount of time you have to work while the mixed resin is still liquidy before it starts to get too thick to pour (or drizzle). For most epoxy resins, this is approximately 20-30 minutes in optimal conditions, 70-80 degrees F. If the room where you are working is warmer than that, you may have less pot time.

In a nutshell, this means you’ll need to work swiftly once you start mixing the resin (but not so swiftly you add in bubbles, of course).

 

 Measuring the Resin Parts:

20150105_220203If you’re using a 1 to 1 ratio resin, pour the first part into the first cup, aiming for an amount to just below the line you marked. If you’re using a 2 to 1 ratio resin, pour the smaller amount first. If you go over the line on your first part, that’s okay, you should have room to adjust the second part. Pour the second part into the second cup also aiming for just below the intended line.

If you’re using a 1 to 1 ratio resin, put the cups side by side on a level surface at eye level (or bring your eye level down to them). Pour the second part into the second cup so the liquid matches at the same amount as the first cup. If you go over a tiny bit with the second part, it’s okay. If you go over a lot with the second part, you’ll need to add the first part to the first cup to nearly match it. Aim for the amounts in each cup to be exactly even. If one is slightly more, it’s better to have the second part slightly more than the first. If the two parts aren’t mostly even, the cure could fail. Naturally, if you’re using a 2 to 1 ratio, you’ll have to adjust the second part to be the right ratio to the first, adding double the over amount to the second cup.

You can use a single cup to measure the parts but then you lose the ability to do a side by side and must be exact when you’re pouring each part . The sides of most medicine cups is angled so you will need to use the measuring marks on the side of the cup and the medicine cups you’re using should be well calibrated.

Epoxy resin is somewhat forgiving and there is some wiggle room in the measure precision (i.e. one part very very slightly more than the other), but it’s best to be as close to the correct ratio as possible for the best curing effect. The resin’s chemicals have been formulated to work best in their designed ratio.

Mixing the resin:

20150105_2203231. If you measured in two cups, the first step is to pour one cup into the other. You can also pour both cups into a third cup (such as one which is larger to give you more stirring room). Scrape the sides of the cup to be sure you get every drop into the cup where you will be mixing. (If you measured both into one cup from the beginning, you can omit this step, of course.)

TIP: The 2 parts poured into a single cup but not mixed will stay separated (like a Tequila Sunrise) because their viscosity is different. You can stage small batches this way until you’re ready to mix them. This will allow you to pour more resin (such as for filling a bracelet mold) while not being as constrained by the same pot time for all the resin. Resin staged like this should be used within a couple hours (or less) of the parts being poured into the mixing cup.

2. Stir SLOWLY. You want to avoid adding bubbles in to the mixture as much as possible. If you whip it up real fast, you’ll end up with resin looking like Alka-Selzer with lots and lots of little tiny bubbles. Slow and steady wins the race. Make sure to scrape the sides and bottom with your stir stick. Also scrape off the stir stick on the side of the cup from time to time as well.

20150105_220359

20150105_220610When you start mixing the resin together, the liquid will appear cloudy or pearlescent (not real easy to see in the picture, but this stage is to the left). As you stir and the two parts become incorporated, the liquid will become clear (as seen on the right). The more you work with the resin you will see this effect for yourself and can use it to know when the resin is mixed.

However, to aid you in knowing how long to stir and remind you it does take a while to mix the parts, set the timer for 2 minutes before you start stirring. It doesn’t hurt, and can help, to stir the resin a little past the time you see it clearing up because there might still be pockets of unmixed.

3. For the ETI epoxy resins (Easy Cast, Jewelry Resin, and EviroTex Lite), they instruct pouring the stirred resin into another cup and continuing to stir for an additional 1 minute to ensure thorough mixing. I usually follow that instruction even with the other epoxy resin brands because it doesn’t reduce my pot time by much and it can help to ensure the resin is fully mixed.

WARNING: If the resin is not fully mixed it will effect the cure and the final product.

4. As soon as the resin is mixed, it’s a good reduce the number of bubbles added in the mixing (no matter how slow you mix some bubbles will appear like magic. I think bubbles are drawn to resin by magnets or something).

20150105_22082320150105_220852 Warming the resin causes some bubbles to rise up like the dead and pop on the surface.

You can let the resin rest for a few minutes (5 minutes is good) in a warm place (like under a lamp).

You can use your directed heat source, such as an embossing tool,  to warm up the resin.

 

Don’t warm the resin too much, though, or you’ll reduce your pot time. If, at this stage, you get rid of the big bubbles that could affect pouring, it’s enough.

Adding Colour:

Colourant = a substance to change the colour of the resin.

There is a wide variety of substances that can be used as colourants both dry and wet. Dry colourants are ground substances, often supplied as a powder with fine particles. Wet colourants are pigments suspended in some type of liquid. All colour comes from pigment binding to the resin. How it binds is dependent on the form the pigment is in when you add it to the resin.

Unless you’re using a pre-coloured resin product, add colourant after the resin is fully mixed. Be careful how much you add. Including too much non-resin in the liquid can impede the curing process. Most pigments are highly concentrated so a little will go a long way.

20150105_221421You can add colourant to resin in a cup. If you don’t want to colour the whole batch of resin, pour a small 20150105_221249amount of the clear resin into a second cup.

  • For liquid pigment, add just one drop (or less) of the pigment to the resin.
  • For dry, use a clean stir stick to scoop up a small amount of pigment and sprinkle it in the resin.
  • Stir the colourant slowly into the resin. You still want to avoid adding bubbles into the resin.
  • Once you have incorporated the first amount of colourant, you can add in more resin or colourant to get the desired colour.

You can also add colourant to the resin on a piece of wax paper or plastic. This is better if you only want to colour a small amount of resin. Smear the resin and pigment (dry or wet) until the pigment is incorporated. Just as with the cup method, you can add more resin or more colourant until you get the colour you want. Try not to add in bubbles with your colourant.

colour2

More comprehensive information on colourants will be in a future blog posts focused on colourants and effects you can get using them.

Pouring:

Sorry for no pictures showing this process. I might need to figure out how to grow a third hand *laugh* I figured out how to get some pictures. Not quite a third hand, just left handed picture taking.

  1. Place your molds, bezels, or other items that you’ll be using on a level surface.
  2. If you’re putting resin into a deep bezel or mold, you can slowly pour from the cup.
  3. If you’re putting resin into a shallow mold or bezel or intend to put a dome on a flat surface, slowly drizzle the resin from the stir stick or a toothpick to control the amount of resin more easily.
  4. Pour or drizzle less resin on the project than you think you’ll need.
  5. Add the resin slowly, both to control the resin amount and avoid bubbles.

PourCompilation

I’ll go more in-depth on using molds, doming, and other pouring techniques in a future post.

More Bubble Management:

20150105_223434After the resin is poured, you can use heat again to get rid of even more bubbles. If your heat source has any wind (blow dryer, embossing tool, blowing through a straw), be careful not to blow your resin out of the bezel, mold depression, or to break your carefully made dome. Careful not to overheat the project.

You can also use a toothpick to draw a larger bubble over to the side of a bezel or mold and pop it there.

A combination of heat and toothpicks will help you cure bubble free.

Clean-Up on Aisle Three:

20150105_224110When you’re finished pouring your resin, you should immediately begin your clean up. Waiting to clean up later will reduce your options and may prevent you from being able to reuse any of the reusable tools.

  • If you’ve used all the resin in the cup(s), you can use wet wipes or nail polish remover to clean off the rest. Leave the cups to fully dry after cleaning them this way.
  • You can also use the wet wipes or nail polish remover on the plastic stir sticks. Leave the sticks to fully dry after cleaning.
  • If you have extra resin, you can leave it in the cup to cure with the stir stick. Once it’s cured to the soft cure stage (6-8 hours), you can usually, using the stir stick, pop it out of the cup. Remaining thin bits of resin can then be peeled off the inside of the cup. The resin then can be peeled off a plastic stir stick.

20150107_065252

20150107_065331

 

 

 

 

The medicine cups and plastic stir sticks can be re-used many times if you employ good clean up. Wooden stir sticks and toothpicks cannot be cleaned for reuse. Plastic cups that bond with the resin (such as plastic shot glasses) cannot be reused.

Curing Stages:

  •  Partial Cure: For most epoxy resins, at 3-6 hours (in ideal temperature conditions), the resin will be partially cured. It will mostly keep its shape but is still a little sticky. If you touch the resin at this time, your fingerprint may be forever captured in your project. This is a good time for a second pour to add in a ‘floating’ inclusion or adding on a thin layer of a colourant you want only at the back (such as a dusting of mica for a background sheen). If you’re working with a mold, you cannot unmold the item at this stage. If you do unmold it, it could lose some of its intended shape as the resin is still an extremely slow moving liquid at this point.
  • Soft Cure: For most epoxy resins, at 6-12 hours (in ideal temperature conditions), the resin will be soft cured. The shape is frozen. Handling the resin won’t leave fingerprints embedded in the surface. The resin doesn’t feel sticky at all. If you brush on a powder, it won’t bond into the resin. But, the resin is soft-ish and can be manipulated before it achieves its final hardness. If you’re using a mold, some molds can be de-molded at this time. If so, when the resin is soft cured, you can trim off unwanted edges quite easily with a pair of scissors. In the soft cure stage, resin has not formed its final, unalterable, bond. It’s possible, in many cases, to remove unwanted over-spills by peeling away the unwanted resin. There are other things you can do to manipulate soft cured resin, but those can be covered in later posts (this one is already too long).
  • Fully Cured: For most epoxy resins, at 24+ hours (in ideal temperature conditions), the resin will be fully cured. This is the point where the resin should feel as hard as glass. The resin won’t change shape at all after this point. It’s solid and frozen permanently. In some weather conditions (or when using colourants) the resin piece will still be a little pliable at 24 hours after its been poured, while safe to demold it may just need some more cure time which can be done after the demolding.

If the resin piece is still pliable 3 or more days after it was poured, it won’t cure any further. Something went wrong in the mixing (or colour adding) or the temperature (and possibly the humidity) was too far from ideal. If  after 3 days the resin piece feels like it has an oil sheen when you touch it, the humidity was too high for the resin formulation. You may be able to save the piece with a second resin pour or by using a resin spray.

TIP: If you’re using a transparent mold, while it is in the late stages of partial cure or later (i.e. it’s not liquid any more), you can view the mold from the underside to get an idea of how the ‘top’ of the resin piece will look when it’s finished. The pictures below show both sides.

FrontToBack

Second Pours:

20150107_064931When the resin has gotten to at least a partial cure, you can add another layer of the same type of resin. If you want to do a second pour with another brand or type of resin (such as UV resin), you should wait until the first pour is fully cured. (The picture below shows the mold flipped over to see how the dark opaque second pour will look, somewhat, on the finished piece.)

Of course, while doing a second pour into a mold, you can also do a first pour into other molds, bezels, etc. to use up the remainder of that second batch.

Dealing with Over-Pours or Spill-Overs:

Once the20150107_064705 r20150107_064832esin has gotten to at least a soft cure and isn’t sticky, if you had any over spills on your flatter molds, you can often pinch off and peel away the excess without affecting the resin in the part of the mold you want. Don’t demold at this point, let the resin get a bit harder.

You can also wait to deal with the spill-overs until you demold the item after it has cured. Doing it at this stage just saves you work later and is easier at this point.

 

Finishing:

Getting items out of molds:

If you’re using molds, you may need to wait a full 24 hours before you can demold. Some, though, will let you pop the project from the mold when it’s cured at least 12 hours and is still a bit floppy.

  • To remove an item from a mold, you need to get “air” between the resin and the mold.
  • Twisting the mold can often break the seal and then pop the item out or peel it out if the mold is shallow.

 

20150107_194828 20150107_194912

 

More information on working with molds will be covered in a later post.

Removing unwanted resin from a cured piece:

A rough surface, like sandpaper, emory board, or a nail buffing/shaping stick can be used to remove unwanted resin from your item. A sanded surface will be matte so you can even use sanding to create effects. If the unwanted resin is thin and/or the piece has not cured to be fully rock hard, you can use a sharp scissors to cut away the large portion of unwanted resin and then sand the edge to smooth it.

Polishing epoxy resin:

Making sanded or matte epoxy resin shiny requires special products. You can use a resin spray or a polishing kit. You cannot buff a shine into epoxy resin like you can with polyester resin.

More information on finishing effects will be covered in a later post (and will include pictures).

 

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Handmade Jewellery by Kate Ledum