I’m working on a Project that Prominently Features a Red PETG Top Surface that after the Printing is done gets Sanded with Grits from 400-2000 +Heat Treatment.
There is a Big Issue tho, After the Sanding is done, I can Rather Prominently see the Walls and Infill of the Layers Below. At first I suspected that I just sanded too much and that the internals weren’t really filled in 100% as they should, but after some testing and Closer Inspection, it just seems the Red PETG is just Transparent enough that I can see the layer below…
So how do I stop this from Happening? Thus Far I played around with Fan Speeds, Nozzle Temps (±10°C), Layer Hight and Ironing all Solid Layers with Mixed Success, non Satisfactory enough however…
To continue using the filament you have, you’ll need more top layers as suggested already. The other alternative is to buy a different brand of red PETG with lower light transmission.
I mostly print in PLA, but there are some brands that are almost translucent while others are opaque after a 0.2mm layer or two and this is all just basic color PLA not anything fancy like silk or the like.
Also you might try lowering the infill. 100% is typically pretty excessive for strength purposes (60-70% is enough) and ironing the top surfaces might help reduce the amount of sanding needed.