These two are close cousins — both glycol-modified copolyesters, both amorphous, both printing in much the same way — and the differences that matter come down to one behaviour and one supply problem.
The verdict: print PETG. Reach for PCTG when the part is transparent, will be flexed or impacted in use, and needs to still look transparent afterwards. That is a narrow specification, and inside it PCTG is genuinely the better material.
Stress whitening is the actual difference
Bend a clear PETG part and a pale, cloudy band appears along the fold. That is stress whitening: the polymer's structure reorganises locally under strain and starts scattering light. It does not mean the part is about to fail — often it is still perfectly serviceable — but the transparency is gone and it does not come back.
PCTG resists this. A cyclohexanedimethanol-modified copolyester deforms without the same optical change, so a clear PCTG hinge, clip or window keeps looking like glass through a working life of flexing.
If your part is opaque, none of the above is a benefit you can perceive. This is why PCTG is a specialist purchase rather than a general upgrade.
What else moves, and by how little
The stored figures are close enough that most of them are not decision-relevant:
| PETG | PCTG | |
|---|---|---|
| Density | 1.23–1.29 g/cm³ | 1.22–1.27 g/cm³ |
| Nozzle | 230–250 °C | 240–265 °C |
| Bed | 70–85 °C | 70–90 °C |
| Deflection | 68–80 °C | 70–80 °C |
| Tensile | 45–55 MPa | 40–55 MPa |
| Shrinkage | 0.2–0.6% | 0.2–0.5% |
| Difficulty | 2 | 3 |
The one row worth acting on is the nozzle temperature. PCTG runs ten to fifteen degrees hotter, which is fine on a modern hotend and awkward on an older one, and it means a PETG profile is a starting point rather than a drop-in.
The difficulty rating differs by a point for reasons that are mostly about how much community-tested advice exists. PCTG is not intrinsically fussy; there is simply far less written about it.
The price of the property
A 90 g transparent cover takes 5 hours on a machine drawing 100 W. Identical overheads apply to both runs — 50 cents an hour for the machine, the American residential rate for the power, and an 8% write-off for prints that do not survive.
In PETG at $24/kg: $5.16 per good part, of which $2.16 is filament. In PCTG at $35/kg: $6.24, of which $3.15 is filament.
Just over a dollar, on a part where a whitened crease would mean reprinting. A dollar and eight cents is the entire premium, and it buys a hinge that will not whiten where it bends — which means the field that decides this comparison is not the price per kilogram but how often the PETG version comes back. Put your own return rate into the failure percentage of the cost calculator.
That is not much in isolation. It is more meaningful across a spool, where PCTG's $25–45 range against PETG's $18–30 means paying roughly half as much again for a material whose advantage most of your prints cannot use.
Where each one is genuinely at home
The stored use lists are short and they barely overlap, which is unusual for two materials this chemically similar.
PETG's list is outdoor brackets, water-contact parts, protective covers and mechanical parts below its deflection range. Every one of those is a job where the material is doing structural work and its appearance is incidental.
PCTG's list is transparent parts, impact-resistant covers, and parts that must stay clear after flexing. Every one of those is a job where the appearance is the function. A machine guard you have to see through, a fluid sight-glass, a display case that gets handled — those are the parts where a whitened crease is a failure rather than a blemish.
Read that way, the decision stops being about which material is better and becomes a question about the part: is its transparency load-bearing?
The supply problem
PCTG is made by a handful of brands and stocked by fewer retailers. In practice this means limited colours, intermittent availability, and a real chance that the product line you standardise on disappears.
For a hobby that matters little. For anyone printing parts they will need to reproduce in a year, it matters a lot, and it is a legitimate reason to design around PETG even where PCTG would perform better.
Shared behaviours you should not have to learn twice
Both materials inherit the same handling quirks, so anything you already know about PETG transfers:
- Both must be dried at 65 °C for 4 to 6 hours. Wet copolyester prints hazy, which on a transparent part ruins the one thing you were paying for.
- Both over-adhere to smooth PEI. Use a textured plate or a deliberate release layer, on both.
- Both string until retraction is tuned, and both droop on overhangs more than PLA does.
- Neither glues easily. Design mechanical joints rather than relying on adhesive.
Getting genuinely clear prints out of either
Since clarity is the reason this comparison exists at all, it is worth saying that material choice is the smaller half of the problem.
Transparency in a printed part comes from eliminating the internal surfaces that scatter light, not from the polymer. That means printing with no infill and 100% wall — vase mode or a solid shell of overlapping perimeters — a thick layer height so there are fewer boundaries, a hot nozzle for good fusion, and minimal part cooling so each bead melts thoroughly into the last.
Get those right and PETG can look surprisingly good. Get them wrong and PCTG will produce an expensive frosted part. Buy the better polymer second, after the process is right.