Silicone rubber yellowing is a concern for many buyers and engineers specifying extrusions. However, while it may look like a sign of material degradation, in most cases it is only an optical effect and not a performance issue. With the right manufacturing controls and expert advice, yellowing silicone can be minimised or avoided. This article explains what causes it, why it matters and how suppliers like Advanced Materials help customers prevent it.
If yellowing is an issue in your current supply chain, contact Advanced Materials to discuss suitable non-yellowing silicone solutions.
What Is Silicone Rubber Yellowing?
Silicone rubber yellowing refers to a visible discolouration that can develop in extruded or moulded parts. It is important to emphasise that silicone yellowing is not usually a sign of material breakdown. Mechanical properties, such as elasticity, tensile strength and compression set, remain unaffected, and safety and performance are unchanged, even when discolouration is present.
So, why does silicone turn yellow? In short, it is an interaction between the curing system and the environment.
Why Does Silicone Turn Yellow? Common Causes
Post-Curing and Manufacturing Effects
Peroxide curing can lead to yellowing silicone during production. Small by-products of the crosslinking reaction can oxidise, causing a colour change. This cannot be reversed after manufacture.
Choosing platinum-cured silicone greatly reduces the risk of yellowing. These grades are often specified in medical, food contact and high-visibility applications.
Environmental Factors
Silicone yellowing can also develop after manufacture due to storage and exposure. The reason lies in the structure of the material. Silicone rubber is porous and has very high gas permeability – it is, for example, around 400 times higher than butyl rubber, a synthetic elastomer (IIR), at 25°C. This means it can easily absorb gaseous substances and microparticles from its surroundings, which can lead to visible colour changes.
Common environmental triggers for yellowing silicone include:
- Formaldehyde released from MDF or OSB wooden boards often used in shelving.
- Chlorine or chlorides present in many cleaning products.
- Vapours emitted from epoxy or polyester-based building materials.
Extended exposure to heat or strong UV can also intensify discolouration, particularly in peroxide-cured grades, although silicone remains more stable than many other elastomers.
| Download our short explainer PDF on Yellowing of Silicone Rubber here |
Why It Matters for Customers
Although silicone rubber yellowing is just a cosmetic effect, it can create problems in industries where appearance is linked to quality, safety or customer trust.
For example:
- In medical devices, tubing and seals must stay clear for visual checks on flow and cleanliness.
- In food and beverage equipment, clear or white extrusions support hygiene perception and product presentation.
- In consumer products, visible yellowing may be mistaken for ageing, contamination or selection of poor-quality materials.
Where aesthetics are critical, engineers and procurement teams often look for non yellowing silicone solutions to maintain a consistent appearance. In practice, this usually means specifying platinum-cured silicone rubber, which is far less prone to discolouration than peroxide-cured alternatives, especially in clear or light-coloured applications. Advanced Materials supports customers in making the right curing choice and provides technical advice on how to minimise the risk of yellowing.
“We’ve seen silicone rubber yellowing arise in everything from food processing lines to medical tubing. It’s rarely a performance issue, but in customer-facing applications even a small colour change can create the wrong impression. With decades of extrusion experience, we know which curing system minimises these effects, and we work with engineers and buyers to ensure the right solution is specified first time.”
– James Randell, Technical Sales, Advanced Materials
How to Prevent Silicone from Yellowing
Choose the Right Curing System
The most effective way to prevent yellowing is to select the right curing system. Peroxide-cured materials are more likely to discolour, especially in clear or light-coloured parts. By contrast, platinum-cured silicone rubber is far more resistant to yellowing, which makes it the preferred choice where appearance and long-term clarity matter.
When deciding between peroxide- and platinum-cured grades, engineers and purchasing managers often weigh up factors such as:
- Cost – peroxide-cured silicone is generally more economical, but can be prone to yellowing.
- Regulatory needs – medical and food applications often favour platinum-cured grades for their purity and compliance.
- Visual requirements – where clarity or long-term appearance is important, platinum-cured grades are usually specified despite the higher cost.
This balance between cost, compliance and aesthetics makes material choice an important early decision.
Manufacturing Adjustments
If peroxide curing is required, there are proven methods for how to prevent silicone from yellowing during production.
At Advanced Materials, our technicians can introduce a very small amount of ultramarine blue pigment at the catalyst stage of mixing the raw material. This balances out yellow tones and produces a cleaner translucent finish with a slight blue tint, without affecting performance.
These adjustments are based on years of extrusion experience and give purchasing managers and engineers practical options to control appearance without compromising the underlying properties of the silicone.
Storage and Handling
Practical measures in warehouses and production facilities also play a role in minimising silicone rubber yellowing. Purchasing and production managers often need to weigh space, cost and operational convenience against the long-term stability of their stock.
Key considerations include:
- Container choice – storing extrusions in gas-tight containers reduces vapour absorption, but requires upfront investment and space planning.
- Shelving materials – MDF or OSB boards are cheaper and widely used, yet they can release formaldehyde that causes discolouration. Metal or sealed shelving is a safer option for sensitive materials.
- Chemical exposure – cleaning regimes and other processes may introduce chlorine or polyester vapours into storage areas. Locating silicone stock away from these sources helps maintain appearance.
- Heat and light – prolonged exposure to heat or direct UV light can intensify yellowing, so parts should be kept in cool, shaded conditions wherever possible.
At Advanced Materials, we advise customers on practical storage choices that balance day-to-day warehouse needs with the goal of maintaining a clean, consistent finish in silicone products.
Can Yellowing Be Reversed?
A common question we often hear from our customers is “how to clean yellowing silicone?” or “how to remove yellowing from silicone?”. Surface cleaning alone is not effective, because the colour change happens within the elastomer rather than on its surface.
Yellowing that occurs during peroxide-curing cannot be reversed. However, when the cause is environmental, it can sometimes be reduced. At Advanced Materials, all of our silicone rubber is fully post cured at 200°C with good airflow for four hours. This drives off absorbed vapours and may restore a clearer appearance, while leaving the mechanical properties unchanged.
The most reliable approach is prevention – selecting the right curing system and managing storage conditions from the outset.
“It also comes down to who you work with. Extrusion specialists who secure quality raw materials can make the difference. Lower-grade compounds, potentially containing impurities, are more likely to show colour changes or inconsistency, especially over time. We’ve partnered with Wacker for over 30 years to source silicone with proven stability, which gives our customers confidence in both performance and appearance.”
– James Randell, Technical Sales at Advanced Materials.
Advanced Materials: Your Partner in Silicone Solutions
At Advanced Materials, we understand that while silicone rubber yellowing is usually cosmetic, it can still be important where appearance matters. Our team works with engineers, production managers and purchasing teams to balance performance with presentation.
We bring decades of extrusion experience and long-standing partnerships with trusted suppliers such as Wacker, ensuring stable access to high-quality raw silicone. That consistency helps reduce the risk of yellowing and gives customers confidence in both mechanical performance and appearance.
In summary, silicone rubber yellowing does not normally affect mechanical properties or safety, but it can be a concern in medical, food, and consumer-facing applications. With the right curing choices and guidance, yellowing can usually be avoided or reduced.
Get in touch if you would like to speak to us about selecting a platinum-cured product, or if you require the addition of blue pigmentation on future production runs.
Advanced Materials is a leading supplier of silicone rubber extrusions. To find out more about our silicone rubber manufacturing services contact our expert and friendly team on +44 (0)1903 713566 or sales@amsilicones.co.uk