Jan 162015
 Published on January 16, 2015

I receive many questions about the use of resin to coat or protect art. Most of the issues faced by artists who coat their art work fall into six categories which I am describing in this article -read on to see what the most common art resin issue are and how to avoid them.

If you are looking for more general information on art resin techniques and uses, make sure to check this article first: How to coat your artwork with resin

The 6 art resin issues

1. Uncured resin can be widespread (none of the resin will cure, leaving you with a sticky surface) or spotty (sticky soft spots or circles are left on the surface of the resin).

  • To avoid curing issues, follow those five steps -all the time:
    • Use fresh resin and hardener
    • Mix resin and hardener in a clean, dry container; pour it in a second container before applying to your artwork
    • Mix the proper quantity of resin and hardener
    • Mix resin and hardener vigorously and thoroughly
    • Cure at the highest room temperature recommended in the resin and hardener specifications (typically 80 °F)
  • To fix curing issues:
    • If the problem is widespread, scrap off the resin and start all over again
    • If you are dealing with soft spots, apply hardener and heat to the problem areas (indirect heat)
    • If you cannot use the above steps, your last two options are:
      • Attempting to cure the piece again in a controlled environment offering the appropriate temperature and low humidity (your kitchen oven will do fine if the piece is small enough). Note that most Epoxies will soften at around 140 °F, which means that the ideal temperature setting is somewhere between 80 °F and 140 °F, depending on what you are trying to solve (uneven curing or slow curing).
      • Re-layering the piece -which is a risky procedure I would not attempt unless and until everything else fails. There is a high risk of eventual delimitation of the new layer because of the instability of the old one. If you are re-layering, you must do so before the base layer is fully cured, typically within 48 hours of applying the base layer.

2. Bubbles are a natural consequence of mixing resin and hardener.

  • To minimize bubbles, you should work with non porous supports -supports that will not generate bubbles or let air flow through. Most wooden art panels are non-porous, but an acrylic sealant / varnish applied to their surface will guarantee that they do not release air into your resin coating.
  • To get rid of bubbles, apply heat with a gas torch during the curing process.
  • For casting applications, use a vacuum chamber to degas the resin or a vibration table after the pour to make sure bubbles move to the surface where you can eliminate them with the blowtorch.

3. Surface bumps are extremely difficult to fix and prevention is the best (sometimes the only) cure. If your surface is non-porous, horizontal and without obvious surface issues, then the most likely cause of surface bumps is that you are not using enough resin -always prepare more than you will need and be generous in your first application.

4. Poorly spreading resin occurs when using a thin layer of resin on a support that although flat and smooth has small areas that the resin will not adhere to. The problem is that those areas can only be detected once you start pouring the resin. In most cases, the solution is to apply more resin; you can also add resin in the problem areas throughout the curing process, so that the new resin is contained to the problem areas by the surrounding and solidifying resin. Another solution is to apply the resin layer in two steps -first a very thin layer, using a plastic spreader, to make sure the resin is adhering to the support. Second, and immediately following the first step, applying a generous s amount of resin to the entire surface.

5. Blushing is a form of water spotting resulting from the condensation and entrapment of moisture during the curing process. It results in dry spots than will appear to be matte (non glossy) or opaque. Sometimes the problematic spots will be milky or slightly white. Blushing can be very difficult to fix but you can usually avoid it by 1) operating with a  dry support and in a dry environment 2) minimizing the curing time by making sure you are working at the right room temperature or by using accelerators with your resin. If you see blushing during the curing process, you can sometimes minimize it by applying constant heat and / or immediately applying a new coat of resin, which may soften the bottom layer and release the moisture.

6. Blooming (sometimes called leaching) is the migration of water soluble chemicals to the surface of the resin. It leaves a waxy residue on top of the resin coat. If blooming is not too severe, it can be cured by simply using lukewarm water to dissolve the waxy residue. Do not use solvents, and never try to sand off the waxy compound itself or you will end up with a gooey mess.

How to avoid art resin problems

How does one avoid those issues in the first place? Here is a checklist to guarantee a successful resin coat for your artwork:

  1. Do not improvise -use known ingredients in a controlled environment where heat and humidity are known and manageable.
  2. Follow the instructions:
    1. Clean containers and mixing tools
    2. Carefully measure resin and hardener
    3. Match the type of resin you are using with the curing conditions of the environment you work in-for instance, do not attempt to do casting work if you cannot control heat and humidity more than a few hours.
    4. Never use resin or hardener that are at or past their shelf life
    5. Mix larger amounts of resin than you think you will need
    6. Seal your art piece before applying resin -brush in or spray an archival acrylic varnish; if using fabric or canvas, seal the back as well.
    7. Keep things simple for yourself:
      1. Work with hard, rigid surface -not canvas
      2. Work on flat surfaces
      3. Do your first attempts with slightly “grippy” surfaces: paper, not vinyl
    8. When in doubt, always test first:
      1. With potentially porous or problematic surfaces -test on a blank before committing to the art piece itself
      2. When first using  certain types of resin -test on a blank
    9. Protect yourself -work in a well ventilated space, use masks, gloves and googles.

Good luck with your art resin project! Let us know how to improve this article or if you are encountering better or different solutions to the problems I listed.