Corrugated plastic - or in the light show world is known as 'Coro' - is the equivalent of cardboard, yet made out of plastic.
If you're in the light show world, and if you're reading this then you very well might be, then coro probably refers to the props you buy and push pixels in.
This product has a lot of other uses - primarily one you see all over the place and never think about - political and small advertisement signs. You might now be thinking 'well that stuff is very different than the hefty stuff my props are made out of' - and you'd be right!
There are many different types of coro - and the type of coro your props are made out actually do matter.
First variance is thickness. If you go to a big box store or even look at the political/real estate signs all around - you'll notice it's much thinner. What is used for most of that is 3.5mm - 4mm. Generally this coro can hold it's shape, but not well - especially as holes get drilled into it.
Ok - so you might be thinking - 'just get the thickest coro!'.
That leads us into the next variance - the flute, or style, of coro. Most of the coro that is easily obtainable (big box stores, sign companies) is "H" flute coro.
It's called this because if you look at a side profile of the coro - the top and bottom of the coro make the sides of the "H" and the internal structure is a series of straight lines that run the length of the coro.
Again, the typical 3.5-4mm coro found is this style. Almost always, the coro from a sign shop is this style as well.
They do make thicker coro, in this style - 6mm, 8mm, 3/8th", 10mm, even 1/2"!
The standard, up until around 2020, in the lighting industry was 10mm H flute coro.
A new product came out - called Correx - which is similar to H flute coro, but it has additional internal bracing in the 'flutes' that shape an "X" in addition to the "H" coro!
This is a huge factor that determines the strength. A 10mm X flute coro is actually stronger than 1/2" H flute coro. Further, the additional internal structure provides additional internal rigidity - which allows for holes to be cut closer/denser.
This became the (high end) standard of coro through around 2021.
4mm "H" flute vs 10mm X flute:
Pixel failures and fires increased significantly.
Polypropolene, which is what coro is made out of, is flammable.
A pixel fire starting in coro means the prop will easily ignite and continue to burn.
This entered in the new version of corrugated plastic, which has a chemical component that makes the plastic flame retardant.
As of May of 2023 - a US based coro company is not able to produce X fluted coro nor provide any flame retardant corrugated plastic. They referred us to a specialty plastics distributor.
The plastics distributor was not able to source anything US made. Nothing.
They were able to provide a sample of a product that is 'certified' to be flame retardant - but in personal testing - once it caught fire it continued to burn.
The coro found at sign shops and big box stores are, almost undoubtedly, US made - H flute and flammable.
There are manufacturers/distributors outside of the US that are able to produce 10mm X fluted coro that is flammable. This is usually purchased in a large quantity (usually a minimum of around 200 sheets) and must go through an importing process.
Ask your coro prop maker, or check their websites - that they carry the best coro - X-fluted, flame retardant coro.
As a show owner who attaches props to our own house - that is what we would want and expect. So should you! That's why all of our props are made from the best.
4MM H flute, 10mm (black) H flute, 10mm fire retardant X flute coro: