by Justin Jimmo
Your clear coat can change your colour.
Clearcoat may be clear, but only compared to your colour coat. If it was completely clear, it would literally be invisible. It’s pretty close, but it still reflects light and refracts light. It’s not completely transparent if there’s light bouncing off it. However, this difference is probably too small to see with the naked eye. So why do the colours change when we add more coats of clear?
Let’s take a look at how building up clearcoat can affect your colour match. Many OEM manufacturers recommend not bringing your first coat of clear right to the edge, because it can change the appearance of the colour and
how it is going to match up to your next panel.
On some colours the effect is really minor, but it can be much more severe on others. In general, two coats likely won’t make a huge difference, but this demonstration will show how the colour can give off a different effect.
A guy I know, Ryan Brown, gave one of the best analogies I’ve ever heard on this subject, so I’m going to borrow it for this purpose.
Think of a swimming pool. Looking in the shallow end, you will observe that it appears much lighter than the deep end. It’s the same liner and the same lighting, so what is changing the look? The answer is very simple. The light has to travel further in the deep end to hit the bottom of the pool. What you’re actually seeing is how long it takes for the light to reflect back at you. In the case of clear coat it’s on a much smaller scale, but the principle is the same. Let’s see what the test reveals.
First, we took an assortment of sprayout cards in various colours (NH678M – Honda Silver, PP4 – Chrysler Jade Met. & PB7 – Chrysler Patriot Blue). Next, we scuffed them quickly and taped off to apply more clearcoat to half of each card. After removing the tape, you can already see the slight difference in colour. Notice how the bottom looks a little bit darker than the top, just like the deep end of the swimming pool looks darker even though we know it can’t be. Our eyes didn’t change, the paint didn’t change. It’s just that the light has to travel further through the clearcoat to hit the base layer and bounce back.
Depending on what kind of light you’re using, the difference can look even more dramatic. Try looking at them in direct sunlight and you’re sure to notice the difference. However, the base colour can affect how much difference we’re seeing. For example, if you look at these particular cards in the sun, you’ll notice that the Patriot Blue looks a bit darker and so does the Jade. The Silver, however, is relatively unchanged in direct sunlight. The shift under the booth lights was much more dramatic in this case. The Silver really reflects the blue mica when out in the sun and still has a bit of a change to it outside.
In conclusion, clear isn’t just clear. The more you spray, the more you’ll end up changing the final colour.
Justin is a Technical Representative – Refinish Sales for Co-Auto Co-Operative. He is also the founder of refinishnetwork.com, an online community for automotive painters. His videos can be seen online at youtube.com/user/jimmo4life.