There can be several causes for defects such as spots or wrinkling on epoxy resin, and in very few cases, the resin itself is to blame.
So what can cause these defects?
High air humidity
The most common factor for the formation of spots, wrinkling of the resin, or creating a skin is high air humidity. It is not recommended to work with resin in high humidity, during rain, fog, or near water surfaces. Ideally, you should work in a dry, warm, enclosed, but ventilated space. If you are working with open windows, you must monitor the humidity in your workshop. A useful tool for checking air humidity is this thermometer with a hygrometer. Epoxy resin should not be worked with at humidity levels higher than 30-40%.
Low temperature
Low temperature, often in combination with the high air humidity mentioned above, increases the likelihood of defects. The recommended temperature for working with resin should not be lower than +20 and higher than +25-27°C. To protect your casts from forming an unsightly film, you can turn on a heater or air heater, but not at full power; the temperature should stay within the recommended range and be consistent.
Excessive use of dyes, additives, and alcohols to remove bubbles from epoxy resin
All dyes and other additives, including bubble removal sprays, should only be used in the quantities recommended by the manufacturer. Always be cautious with additives that you are using for the first time: it is advisable to test them on a small amount of resin first to see how the material reacts to the specific product used. Never use dyes containing water, as this could irreversibly damage your product and even cause an exothermic reaction. Also, do not use dyes containing silicones or oils.
Use of large gas burners with replaceable cartridges
These burners emit more carbon dioxide during operation, which can also cause an unwanted film to form on the resin. It is recommended to use small handheld torch lighters: they are more convenient and safer.
What to do if you are working with resin in an area with high air humidity or have low temperatures in your workshop?
1. Equip your workshop with air conditioning or other methods for regulating temperature and humidity in the room where you are working with epoxy resin.
2. Work and let the resin cure near heat sources.
3. Pre-catalysis technique is another option, but we recommend it only for experienced users. This technique involves letting the mixed resin sit in the container until it starts to heat up, and then pouring it into the mold. This is a controlled exothermic reaction where it is crucial that the resin does not reach a very hot stage and boil over. Using this method will reduce the likelihood of humidity or low air temperature ruining your work and creating an unwanted film on the surface. Ideally, use this technique for smaller amounts of resin (up to about 100 grams), as larger volumes could result in a rapid reaction and you might miss the window for pouring.