Reducing Bubbles in Resin

Updated: Feb 15

Preventing bubbles in resin is mentioned in each of the ArtWorks Resin and Liquid Diamonds Casting Resin product information tabs on our website. However in this blog, I will add some additional information that may also be helpful.

First of all, bubbles are a very common thing. There are so many things that can cause it, and sadly it's not always obvious what did cause it. Trying to learn the ways to avoid creating them, might not be as quick and easy as we'd like, but they are the best way to reduce bubble issues occurring in cured pieces. Once people have it figured out, they produce beautiful results more regularly. Note that even pros with 10 plus years experience have set backs now and then. All resins do behave a bit differently than each other. If you're used to doing things a certain way with one resin, you may need to change the processes a bit for best results, with each type used.

More common causes of added bubbles are:

. Mixing too quickly.

. Cold resin, room or items used in process including substrate or moulds.

. Resin is reacting to something added to it, sprayed on it or possible contaminant.

. Bubbles often release off of items when adding an inclusion in to the resin.

Here are some areas to consider for reduced issues with bubbles:

1. Temperature is a huge factor with epoxy resins. You will always have best results in a consistently warmer/ambient room (from start though to cure).

There is always certain times of the year, that people who never had a problem before, all of a sudden have a problem. And more often than not, it is interesting when we check for weather changes in their location, that is often what we see (even when a person states they keep their space at a certain temp, it is possible for humidity changes to effect resin as well). A temperature of 21C to 26C (70F to 77F) degrees is best for working in, and throughout curing process.

Our colder climate weather (in Canada) poses challenges for keeping rooms ambient for resin projects. Thanks to a recommendation from a 10 plus year resin artist, I bought a heating unit that works great in my application. The unit recommended is ideal for not blowing air into the space, and it self regulates the temperature. I have in-floor heat that keeps my basement space warm in the winter, however in the summer & warmer days, my basement studio has the in-floor heat off, so I require a space heater to keep it warm during the entire process, through to cure. I added the type of heater recommended to me at the end.

Occasionally people suggest using a heat type mat if in a cold area. Some people have made set-ups for keeping their projects warm during cure. Ideas like using a plastic tub with a heating blanket underneath. We’ve seen well-meaning people getting creative putting heat lamps, space heaters, etc too close to their cups or other epoxy resin projects, trying to get them to dry faster. Sure, this will speed up the drying process... Not the curing.... but the drying. But these more direct heat methods can also cause pre mature yellowing on your cups/projects. Please keep that in mind.

***Important note: Heating the room or area is great. Direct close contact heat is not ideal, & it is not the same thing.

Tip: Buy & regularly use an infrared thermometer. You can aim it directly at your resin bottles, substrate, mould, etc., to see what the actual temperature is (instead of guessing or assuming). If you start to make notes of the information, you can track what works best for you in your space (what works best is often different for each person, and remember weather changes can effect the way things are done too).

2. Sometimes people want to use one type of resin for every type of project, but depending on what projects you do, this may not give you the best results possible. A casting resin such as Liquid Diamonds is best used for creating projects in moulds. It's thin (like water) viscosity, helps keep the bubbles to a minimum, and when bubbles are formed, they dissipate easier in the thinner resin. Thicker resins, like ArtWorks, are great for doming projects, topcoating, and resin art creations, however thicker resins absolutely do have more bubbles. We have customers that do choose to use the top-coating resins (they like ArtWorks faster cure time), occasionally in moulds, but they should only be used for casting in less than 1/4" layers per session, (keeping In mind top-coating resins are meant to be used at about 1/8” depths). These customers have played with it enough to know how to reduce the bubbles ahead of time. The bubbles need to be able to travel up and out, and the thinner viscosities enable that better.

3. If your resin is cold to begin with, it will bubble more In mixing (especially thicker resins like ArtWorks). Many people find warming up Part A of the resin, can help. Some people use warm water in a sink or bucket to do this. Ideally, put your resin Part A container in to a plastic bag before setting in a bucket, tub or sink of warm water. If I don't have a bag, I ensure I thoroughly dry the container off before pouring resin out, as any little moisture drops of water from container, can ruin your resin cure. Some people need to warm both containers Part A & B if the resin & hardener are extra cold. Some people set their resin containers & mix cups, on a heating blanket, or near a heater to warm it up prior to working with it.

***When doing any type of warming up the resin, don't overdo it. When warming up resins, it can shorten your pot life with both viscosities of resin. With thicker resins, you can also cause the chemical reaction to occur too quickly if you've warmed it up too much. Keep in mind, when you warm Part A & B, you will reduce your pot life and speed up the cure process. Even just warming up Part A can still shorten pot life if warmed too much. Ideally use warm tap water, (apx 15 minutes should work) not hot water. If it starts to warm up and thicken in the mix cup, it is known as premature exotherm. Premature exotherm can cause a variety of extra issues. One issue, is it can cause is unnecessary added yellowing. Another thing it might cause, since it's now almost in mid-cure, is it may not bond correctly. There are others discussed in the main tips blog.

4. We discuss mixing thoroughly, but gently in our instructions. Mix for 4 mintues, or until all the striations are gone, occasionally scraping along the sides and across the bottom. Many people find using non-wood stirring tools creates less bubbles, since wood is porous. Using a plastic or silicone or steel stirring tool is often suggested for less bubbles. When making larger batches, it is harder not to introduce bubbles.

With Liquid Diamonds, we recommend letting mix cup sit for about 5 minutes for bubbles to come to the top and dissipate prior to pouring gently into moulds.

With ArtWorks being a thicker viscosity, we do NOT recommend letting it sit in mix cups, rather getting it out on to the substrate as soon as possible to get most pot life time out of it. If you leave ArtWorks sit in the mix cup, you will encourage it to begin the cure process sooner than it should (premature exotherm).

In either case with any viscosity, know ahead that you will need to have a way to get rid of any bubbles once you have finished with your creation(s), before leaving them to cure.

5. Are your surfaces cold, that you are putting your resin into or on? Temperature differences can produce surface tension, which could cause bubbles to get trapped during pouring. If working with moulds that are oven safe, you can gently warm them (at about 150F) before using, or you can slightly warm substrates/tops/moulds/bezels etc with a low setting on a heat gun, or warm hair dryer. Keeping in mind moulds do not like to be overheated, do this very carefully. We have a separate blog about mould care. For most top-coating projects, it is quite easy to pop bubbles that come to surface, but if they're trapped under from the surface tension of substrate being cold, it is trickier to catch them. If the surface resin begins to cure while those bubbles are still underneath, it is too late.

6. In moulds, some people use a dusting of complimentary mica powder to help decrease the surface tension of a mould. Or some use a fine dusting of baby powder, which they say can help reduce the bubbles close to the mould. Keep in mind this effects the resin shine to dull as well. if wanting to use this method, use a soft & delicate paint (or better a makeup) brush to dust the powder in, then tap out any extra (from the mould), before pouring resin. This is not something I have personally done, but I have seen recommended by numerous casting artists. If you choose to try this method, practice on smaller pieces first. When ever trying anything new, it's best to practice on smaller pieces to get the hang of how it works for how you use your products.

Another way to break surface tension, is to roll the resin around your mould/bezel before completely filling it. If there are any bubbles showing at that time, it will be easier to pop the bubbles now, because there is less vertical space for them to move around in or get trapped under other resin. And for more intricate moulds, you may need to pick them up and manouver them around several times during pouring resin in.

7. Any additions or inclusions can be another huge source of adding bubbles. They each can also have their own source of additional surface tension, or potential oils from fingers, or other possible contaminants that may get added to a piece. Sometimes the issue comes from contaminated tools. For some inclusions, it can be necessary to dip inclusions in resin prior to adding them into your mould/bezel to help break surface tension on those. Once you have dipped them into resin, put them gently into your mould/bezel on an angle, then carefully slide into place. When putting inclusions flat onto resin surface, you can easily trap bubbles underneath (they may or may not move outward during cure).

8. Once your current resin session is done, go over the piece with a heat source to pop remaining bubbles. If it's a casting, we recommend a barbecue lighter with adjustable to low flame, using caution. Do not allow flame to touch resin or come near mould. Some artists prefer using an embossing heat gun, or other gentle heat sources. Sometimes heat guns can blow dust or hair in the air into your piece, or the airflow can move your design off. We prefer to recommend the barbecue lighter gentle flame option. Another thing to be aware of with the heat gun, is some artists suggest use of a heat can start to cure the resin from the top, so you may be trapping the bubbles within.

If it's a topcoating and larger type piece, use a propane torch with a wider flame thrower, and again, keep the flame from touching the resin or any surface. The butane chef torches can be used, but they tend to throw a pointy direct flame, so using it on a slight angle (if piece is wide enough) may save accidental singeing of resin. These chef torches are not ideal for moulds due to the pointy direct flame.

The c02 from the flame is what pops the bubbles so there is never a need for flame to touch any resin or surface area. If you overheat it or singe the resin, it creates undesirable results in the cure. Another option I have mentioned if bubbles are at the top or sides of the mould, you can try to push them in to the middle to pop with heat, or heat a sewing needle with a barbecue lighter and try to pop bubble without the needle touching the mould. Or, if it's high viscosity resin, you can use a syringe and large bore needle to suck up the bubbles carefully.

Some people like to use a light misting of alcohol to pop bubbles, many resin manufacturers do not recommend this, as it could negatively affect the cure with pinholes or a splotchy finish (so be aware while it may reduce bubbles, it may possibly effect finish). Sometimes overheating/ overtorching can cause wrinkles or crinkles in your finish. Be aware, certain colourants can also be responsible for any added oily residue on cured finishes.

Some people like to set their work on or by a light box (depending on type of mould), to help check for bubbles before leaving piece to cure.