Why Does Epoxy Resin Hardener Turn Yellow/Amber Color Over Time? (2024)
If you’ve used epoxy resin in the past, you may have seen the hardener part discolor in the bottle over time. This phenomenon is called ambering and caused by oxidation. Although this is not necessarily a sign of degradation it’s useful to understand why it is happening and how it can potentially be prevented, or at least slowed down for water clear application.
Ever cut an apple in half and it slowly turns brown? That’s oxidation, and yes, it’s still perfectly fine to eat! Same goes for epoxy resin hardeners. A chemical reaction occurs when both apple flesh and epoxy resin hardeners come in contact with oxygen. In short, that complex chemical reaction causes an ambering effect. The taste and nutrition of the apple is unaffected and the curing process and strength of the epoxy resin also remains the same. Oxidation is only a shift in color and nothing to get overly excited about.
With prolonged exposure, as well as additional oxygen introduced into the epoxy hardener bottle after pouring some out, the hardener will oxidize more and turn a darker shade of amber, or even brown over an extended period of time.
Does Oxidation Really Matter?
As all epoxy brands are not created equal, some brands use low grade chemicals that oxidize extremely quickly. Years ago Greenlight used to distribute a certain brand of epoxy resin (which will remain nameless) but when a full drum of hardener arrived to us looking doo-doo brown we started investigating why and learned a lot about epoxy chemistry. We ended up selling that resin at a loss to get rid of it and started the task of developing our Marine Grade Epoxy Resin System using the highest grade chemical compounds available (and some special sauce) to improve epoxy surface finish through eliminating pin holes, fish eyes, and orange peeling which are typically a big problem. The use of high grade chemicals shows to oxidize much slower than cheap materials but the hardener will still turn amber over time. It’s just the nature of epoxy chemistry…
When mixing an oxidized amber tinted hardener (Part B) with the epoxy resin component (Part A) will reduce the amber color to be barely noticeable, especially when applied in a thin layer as in a fiberglass lamination or an epoxy sealcoat.
So, no big deal if your epoxy hardener turns yellow, amber, or even brown color in the container. It’ll still have the same strength and durability as fresh resin. If you have really old epoxy hardener that has turned brown you can always add an epoxy pigmentto color the resin and have no issues at all.
Curing is a chemical process employed in polymer chemistry and process engineering that produces the toughening or hardening of a polymer material by cross-linking of polymer chains.
https://en.wikipedia.org › wiki › Curing_(chemistry)
agent or "hardener" can change in color over time due to several factors, including the shelf life, chemical reactions, exposure to light, temperature, and moisture, and the presence of impurities. These different factors can cause the epoxy hardener to become yellow, orange, and even brown over time.
First off, it's all about oxidation - think of it as your hardeners way of taking a deep breath of air. Once it's manufactured, this oxidation journey begins. 🌬️ It's like an apple turning brown; totally natural but not always what you want.
Some resins may take only a few days of direct UV exposure to start turning a clear resin to an oxidized yellow while others may take months to notice. It is an effect that oxidizes and degrades more and more over time.
Resin yellowing is mainly due to the change in molecular structure caused by hydrothermal or UV radiation, leading to the change in color and mechanical properties [28].
If you do notice that the color of the applied epoxy resin still has a yellow hue you can add a small amount of Deep Sea Blue Liquid Resin Dye to mask the color of the yellow hardener. Otherwise, it's probably best to replace the product if you have any concerns of your projects final clarity.
It's important to prevent yellowing by using UV-stabilizers and inhibitors, storing the hardener in a cool, dry place and using it as soon as possible, and controlling the curing environment.
hardener component: The hardener component of epoxy resin usually contains amines or amine compounds. These amine compounds can also contribute to yellowing, especially if they react with UV radiation or chemical compounds in the environment.
ArtResin epoxy resin is properly stabilized against the degradative effects of oxidization and UV light to prevent and significantly delay yellowing, aka ambering, aka browning.
A resined piece that is placed outside will generally reach its dark brown-yellow color within 24 hours. Artwork that is kept indoors will begin to discolor generally within 6 months to a year if it was coated in a resin product that contained only a UV stabilizer.
Once the epoxy has turned yellow, there is not much that can be done to reverse the discoloration process; however, it is possible to reduce its impact and prevent the epoxy from yellowing even further. Epoxy hardeners can also experience a yellowing discoloration that compounds the epoxy's off-color issues.
Discoloring in a small area of your epoxy floor or on the first layer may be a simple fix. While some tips suggest cleaning discoloration with bleach or steam, it's best to let an expert handle the problem. A professional can recoat the flooring after proper maintenance, leaving your floors looking as good as new.
A simple way to see if your yellowed epoxy is UV-damaged or simply dirty is to clean it! Just a mild cleanser and warm water is enough to clean epoxy surfaces. While there is no way to reverse UV-exposure in epoxy resin, you can massively aid in its prevention before you install epoxy!
Use a fine-grit sandpaper or a floor sander to gently sand the yellowed areas of the epoxy floor. The goal is to remove the discolored top layer and expose the fresh, unaffected epoxy beneath. Be careful not to apply excessive pressure or sand too deeply to avoid damaging the floor.
The shelf life of MAS epoxy resins and hardeners is at least one year in sealed containers, but the material can last much longer when stored between 60-90°F in a dry place. The product should be stored indoors, on a raised surface off the floor and away from exterior walls.
Introduction: My name is Msgr. Refugio Daniel, I am a fine, precious, encouraging, calm, glamorous, vivacious, friendly person who loves writing and wants to share my knowledge and understanding with you.
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