How to Fix Yellowing in Epoxy Resin

Troubleshooting Yellowing in Resin: Causes, Prevention and Restorative Method 

You have spent hours for creating a clear and shiny resin piece, only to notice it yellowing over time - a frustrating experience for any resin artist or maker.

One of the most prevalent problems of epoxy resin, regardless of what you are making jewellery, coasters, river tables, or artwork, is yellowing. However the good news is that once you know how and why it occurs, why it can be prevented or remedied, you will have your resin projects remain crystal clear during the years.

Breaking down the causes, prevention measures and restoration alternatives of yellowing resin step by step.

Why does the resin turn yellow?

Even excellent quality epoxy resins may turn a little yellow with time, yet there are other circumstances that accelerate the progress at an extreme rate.

UV Exposure

The number-one culprit.
Exposure to UV light in the sun or fluorescent bulbs disrupts the chemical bond itself in epoxy leading to oxidation and the appearance of yellow colour.

Common signs:

• Surface fading/amber discoloration.
• More evident on white or transparent works.

Temperature and Thermal Instituteability

Storing or Curing resin under hot conditions causes oxidation to be quicker.
Regular warmth (such as that around a radiator or window) may cause the resin to age more rapidly.

Bad UV Inhibitors or Inexpensive Recipes

Low-cost resins do not include UV stabilizers or optical brighteners that inhibit color change. In their absence the resin darkens naturally with time.

Contamination

Using tools, moulds or pigments that are not clean or cannot be used with epoxy may cause impurities that colour the resin.

Improper Mixing or Ratios

Excessive hardener or lack of even mixing leads to chemical instability and your resin will cure with a yellowish color immediately.

The Yellowing Prevention

It is very much easier to prevent than restore. This is the way you will prevent your new resin project from turning yellow too soon.

Choose a UV-Resistant Resin

Find UV-stabilized/non-yellowing epoxy (such as Epoxy Res-iT Premium Clear).
Such formulas contain UV absorbers and HALS (Hindered Amine Light Stabilizers) which are active in photo-oxidation prevention.

Avoid Direct Sunlight

Resin pieces should always be cured and stored in the shade and a cool place.
When it is displayed close to the window, UV-filtering glasses or acrylic covers can be considered.

Measure Accurately

Apply accurate proportions of resin to hardener (i.e. 1:1 or 2:1 according to formula).
Wanted tinting can be caused easily by inaccurate mixing.

Use Clean, Compatible Tools

Clear resin can be tinted with polluted cups, mixing sticks or old pigment.
Isopropyl alcohol wipe tools are used but allowed to dry completely before use.

Top-Coat UV-protective Sealants

A coating of a UV resistant varnish or clear finish can be used to offer an added protection to works subject to light, including tables or wall decorations.

Res-iT Tip: The Epoxy Res-iT Protective Gloss Topcoat is a durable UV barrier that maintains its clarity, which is best applied to furniture and pieces of decor.

How to repair or minimise it

In case your resin has already been yellowed, do not panic. It will depend on the depth of discoloration and the nature of the project you are working on, how much will be recovered.

Surface Yellowing

In case it is light and confined to the surface:

• Lightly rub with fine-grit paper (1000 -2000 grit).
• Clean with alcohol wipes.
• Coat with a thin fresh layer of UV stable resin or clear coating.

This tends to bring back the light and shine.

Moderate Discoloration

For more visible yellowing:

• Attempting to neutralize the amber color, a drop of blue or violet color can be added to produce a clear color.
• Wipe the finish off or re-polish the surface.
• Cool solution to using faulty pours.

Severe Yellowing

In cases whereby the resin has stained in all parts, complete restoration might not be ensured. In this case:

• Sift and re pour a fresh coat on.
• Prep as a foundation to new artwork or practice mould.

This reduces wastage and allows you to make up the experience.

Perceiving Realistic Expectations

Even the highest quality resin may acquire a slight amount of warmth in several years. It is normal and in the nature of epoxy and what the aim of the process is to slow it down as much as possible.

To keep pieces clear:

• Limit sun exposure
• Store at room temperature
• Wear topcoats and UV stabilizers.
• It should not be subjected to high-heat curing conditions.

When well kept, professional resin such as Epoxy Res-iT Pro Kit will be clear over many years without some apparent yellowing.

Recommended Products to Prevent Resin Yellowing

View the entire line of the non-yellowing resins and protective topcoats of Epoxy Res-iT on our web site, developed to be long-lasting and clear.

Frequently Asked Questions

Why does epoxy resin become yellow with time?

The main causes of the yellowing of resin are UV light, heating, or the absence of UV stabilizers in the formula. Inexpensive resins which are not properly inhibited oxidise more readily resulting in amber tones.

What do I do to avoid the yellowing of epoxy resin?

Apply an epoxy resin that has UV-stabilizers, put pieces that are already finished in places that are not exposed to direct sunlight, and apply a protective coating. Care must also not be overheated during the drying.

Is it possible to cure yellowing of cured epoxy resin?

To fix minor surface yellowing, sanding, polishing or applying a UV-stable layer can be done. Prolonged inward yellowing is however not normally reversible.

Is epoxy resin getting yellow all the time?

Any resin can exhibit a case of slight warm color over a long period, although high quality and UV resistant resin such as Epoxy Res-iT Pro Kits can greatly retard the rate of yellowing.

Which epoxy resin is best in the prevention of yellowing in the UK?

Select an epoxy containing in-built UV blockers and HALS. The epoxy resin Res-iT Premium Clear and Deep Pour Resin are meant to withstand the effects of yellowing in the UK environment.

Final Thoughts

Yellowing of the resin is not unavoidable but disappointing. With UV-stabilized products, a clean workspace, and careful storage of your resin creations in the heat and sunlight, you can have years of crystal clear and professionally looking resin creations.

We make Epoxy Res-iT UK non-yellowing, high-clarity epoxy systems which are chosen by artists, makers and DIY users that are interested in the quality of their work to last.
Nothing less is due to your art.