We've noticed someone saying that black PETG blanks contain ‘carbon’ that breaks diamonds. To put it simply, this just isn’t the case but like most rumours, once it starts going around, it sticks. So, as we love to give out all information ….here’s what’s actually going on.
Black PETG is exactly the same material as clear PETG. If anything that was put into the PETG changed the structure and the way it behaved, it simply wouldn’t be PETG anymore. The rules for plastics are strict! So it’s still polyethylene terephthalate glycol-modified, the same base polymer, the same chemistry, the same physical behaviour. The only difference is that black PETG has a small amount of colour added (around 2% to 5%), and that colour comes from carbon black pigment, not a structural filler.
That distinction matters. A pigment’s only job is to give colour. It’s used in tiny amounts, usually just a few percent of a colour ‘masterbatch’ blended into the base resin during extrusion. A filler, on the other hand, changes how a material behaves. Below is the technical specifications of our PETG, as you can see, all variants and colours are identical, this is the data and the science. So to make it clear, pigment doesn’t change the way the plastic cuts, melts or flows. It doesn’t make it harder or more abrasive. It just makes it look black.
Furthermore, the carbon black pigment itself is extremely soft. It’s amorphous carbon, not crystalline graphite or anything remotely hard. On the Mohs scale it’s about a one or two, compared to diamond at ten. Even if the pigment existed as loose particles, which it doesn’t, because it’s fully embedded inside the polymer, it would be far too soft to scratch or chip a diamond tip.
The science is straightforward. Opinions are misleading and as always, we are happy to share the actual technical specification. We’ve now sold over 30,000 black blanks in the past 12 months. Don’t let bad information get in the way of good cuts.