Why Do Surfboards Go Yellow? Explained By Science

why-do-surfboards-go-yellow

The primary cause of surfboard yellowing is UV radiation from the sun. It’s the same way that the sun turns you a lovely shade of lobster red when you get sunburnt.

However, other factors all play their role in turning your trusty steed yellow over time. And we are going to look at each different part in this article.

15-second summary: 

  • Discover how the sun’s UV radiation causes a chemical breakdown of the surfboards resin. 
  • Find out why heat also causes a reaction with the epoxy in the board
  • Look at some preventative measures to prolong the onset of yellowing
  • Finally, find out why the Silver Surfer’s board can never turn yellow.

Let’s begin! 

How the sun turns a surfboard yellow

To answer this, we first need to know about the two main molecular structure types of resin, and these are;

  1. Aliphatic – (Strong) structure is typical of urethane resins but consists of chemicals not friendly to surfboard foam.
  2. Aromatic – (Vulnerable) is found in the vast majority of epoxies on the market today.

The structure found in surfboards is Aromatic, which is the weaker of the two.

Okay, so now that we know surfboard resins have a vulnerability to UV light. But what happens when UV radiation comes into contact with the resin.

The energy delivered by the suns photons begins to break down the molecular structure of the resin. This same process that we referred to earlier in the form of sunburn.

So with the structure breaking down, the chain molecules that break away are known as free radicals (a carbon molecule in this case).

Now, this is where the yellowing begins because these free radicals need something to bond to. And what they attach themselves to is oxygen, which causes a new compound that is yellow.

Does heat turn a surfboard yellow?

In short: yes. Exposing a surfboard to extreme heat over long periods will cause damage due to the gasses inside the foam core expanding.

But yellowing from heat is caused by something called Exotherm. Which is a reaction that gives off heat during its formation. In this case the resin and the hardener/catalyst.

What this does is cause the mixture to chemically heat and begin to break down the molecular structure in the same way. However, it is not as effective at breaking it down as UV radiation.

If we think of cheaply manufactured surfboards getting made with large amounts of epoxy resin mixed at the same time. Less care is taken in keeping Exotherm to a minimum through careful mixing.

Mass-produced surfboards will begin to yellow sooner than custom boards (with resin explicitly mixed) because the breakdown process has already started sooner.

How to prevent surfboard yellowing?

Before we answer this question, we must accept that it is impossible to stop yellowing. But we can slow it down and prolong the clarity of the resin.

  1. Use UV absorbers: These can be added to the resin mixture. They work by providing the free radicals something to bond to. However, there are only a finite number of absorbers available, and eventually, there will be more free radicals than inhibitors, and yellowing will start.

  2. Limit Exotherm: this is difficult to do if you are not the one mixing your own boards resin. But being careful with the micing ratio and amount of resin will lead to a better end finish.

  3. Use surfboards bags or covers: Using surfboard bags and socks is a great way to extend its lifespan and keep it out of harmful UV rays when not in use. Why not have a look at some of the best surfboard bags on the market.

Why the Silver Surfer’s board will never yellow

By default, the Silver Surfer rides around space in a vacuum where there is no air.

Remember, a free radical bonding to oxygen in the air is what causes yellowing.

So even though his board is exposed to UV radiation, just like ours. Yellowing cannot happen because there is no oxygen available for the free radical to bond to. And there you have the answer, science. Boom!

Final Thoughts

Unfortunately, yellowing is just a part of surfboard chemistry. All you can do is slow it down.

But using science in the manufacturing process can produce a product that’ll keep its shine for longer.

Proper surfboard care also goes a long way in keeping that manky yellowing away.

If you want to store your board in ways that’ll help prolong its lifespan, check out this article.

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