PETG stands for glycol-modified polyethylene terephthalate – similar to PET, which you may know from plastic water bottles – but an additional glycol is included in the polymer structure, hence the letter “G” after PET for “glycol-modified”. The result is a clearer, less temperature-sensitive material that’s easier to extrude than PET.

There are more variations of PET in filament than just the familiar glycol-added version, and all of them share many properties but with some important differences.

• PET: Polyethylene terephthalate (PET) is one of the most commonly used plastics in the world and the unmodified parent of PETG. It melts at 260 °C and has the most potential for recycling – local program permitting. PET struggles more with layer adhesion compared to PETG.
• rPET: Exactly the same as its base material, PET, but this filament gets a lowercase “r” in its name because it’s made from recycled PET. Previously recycled materials may not be recyclable again, at least not with the same results.
• CPE: Some brands choose to differentiate PET products with a moniker. Fillamentum and UltiMaker use “CPE” because it stands for copolyester.
• PETT: Polyethylene co-trimethylene terephthalate is slightly more rigid than PETG because it isn’t modified with glycol. It isn’t very common in 3D printing but was popularized by Taulman T-Glase.

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PETG is a good all-around material but stands out from other filaments given its flexibility, strength, temperature, and impact resistance. Let’s take a closer look at the properties of PETG filament.

Strength

PETG is an excellent filament choice for printing objects that need to be sturdy, smooth, and exhibit low shrinkage.

Compared to the other entry-level filaments (e.g. PLA and ABS), PETG is often the best choice for prints that need to withstand impact and shear forces. While ABS and PETG are both stronger and more durable than PLA, PETG can offer some flexibility that would snap ABS in half.

While it isn’t the strongest filament material out there, PETG is well-suited for many moderately demanding applications. It’s ideal for objects that might experience sustained or sudden stress, like tools, 3D printer parts, and protective casing.

Durability

Despite PETG’s strength, it’s more prone to scratching and surface damage compared to PLA. And while PETG fares better outdoors than UV-sensitive ABS, it’s still prone to degradation in the long run. (Parts may last about a year outdoors.) PETG is temperature resistant up to about 70 °C – better than PLA but not as great as ABS.

Like its cousin PET, PETG can provide a good barrier to moisture and can even be used to print parts that hold water for extended periods like vases or planters.

Food Safety

PETG is generally considered food safe, but you should check with the manufacturer to ensure that their processing conforms to food safety standards. Check out our article on food-safe filaments for a few PETG options that fit the bill.

Moreover, if you plan on printing kitchen items with PETG, be sure your printer, extrusion system, and nozzle (avoid brass) have been cleaned thoroughly.

Hygroscopy

PETG is hygroscopic, meaning it will absorb moisture from the air, which causes all sorts of problems that mostly culminate with a disappointing failed print. Be sure you keep PETG stored in a dry environment, whether it be a DIY or purchasable dry box. For best results, dry PETG filament prior to printing.

Recycling

Although related to the commonly recycled PET, the chemical modifications to PETG do have the unfortunate side effect of changing the recycling process. The subtle differences between these materials create a troublesome contaminant in traditional recycling facilities.

While you can’t throw PETG scraps into your household recycling, PETG is still recyclable. You can try sending PETG scraps to a recycling service or building your own filament recycler system. However, if those options are too large-scale for your current operation, you can also purchase recycled PETG filament to reduce your consumption of virgin materials.

It’s true that, despite being comparable to PLA for its ease of printing, many makers do find PETG a bit trickier to print than other materials. PETG certainly has its quirks, so you’ll need to find the “sweet spot” for your print settings.

Temperature

The ideal temperature settings for PETG filament will vary depending on the specific filament and manufacturer, but the material is generally pretty forgiving.

The print temperature will usually range between 220-260 °C. You can tell if the temperature is too low when the first few layers don’t feel a little greasy. If you plan to print PETG a lot, consider upgrading to an all-metal hot end as prolonged periods at these temperatures will degrade the PTFE lining in a PTFE hot end.

Manufacturers will often recommend a print bed temperature between 50-80 °C. A heated bed is essential for promoting bed adhesion, especially when it comes to avoiding warping on the bottom of large-scale prints. You can also try glue sticks or blue tape.

Speed & Retraction

You should always start with a low print speed of around 15 mm/s and work your way up. Printing at this low speed will help you sort the other settings like temperature out, after which you can start increasing it. However, setting fast travel speeds (non-extrusion movements) can help prevent stringing.

Speaking of stringing, you’ll likely find PETG is particularly prone to such behavior as well as clumping at the nozzle compared to other filaments. This makes turning the retraction settings key to minimizing the post-processing of PETG prints. You’ll want to start slow here too – exactly how slow depends on the type of extruder – and use retraction test prints to dial in the right settings.

Cooling 

PETG prints best at low fan speeds, around 25%, but some may get away with no fan at all. For the initial layers, turn off cooling to improve bed adhesion.

PETG exhibits better layer adhesion than its competitors, but it may adhere to itself too well, leading to its issues with stringing. Due to this inherent stickiness, PETG isn’t great at bridging and overhangs, so upping the cooling a bit on these features may improve results.

Like PLA, PETG is excellent for low-warping, showing only minor shrinkage during cooling. If you notice warping or layer adhesion issues, it’s probably a sign that there’s too much cooling.

All You Need to Know

The PETG Print Settings for Perfect Results

While filaments like ABS can offer solubility in acetone, which is great for creating an unbelievably smooth finish, post-processing PETG is not so hands-off. If you’re going for a fresh-off-the-injection-mold look with PETG, you’ll have to opt for some manual methods. This typically includes sanding and a clear coat to give it a nice shine.

PETG generally doesn’t like to be painted, so if you’re planning on using PETG to print a cosplay outfit or board games, be sure to use a primer first.

More on Painting

Painting PETG, PLA & Other Plastics – 4 Methods

Once you’ve settled on using PETG for your print, you’ll need to choose a blend. There’s a lot on the market, but if you’d rather not slog through the web to find a good one, we’ve narrowed down a few options for you:

Eryone

This mid-range PETG filament is a great go-to pick for everyday printing with 10 color options to choose from, including a few transparent versions. We’ve found it to print consistently with good dimensional tolerance.

Eryone also offers carbon fiber-infused PETG, which uniquely comes in a few more color options beyond the typical black. You can often find 1-kg of their PETG for under $20 at Amazon and the carbon fiber PETG for a few bucks extra.

Eryone PETG

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FormFutura

This brand offers both a transparent, high-gloss PETG called “HDglass” as well as ReForm rPET, which is made from recycling excess material from the production of HDglass. Despite the recycling, the filament prints easily – it’s almost PLA-like.

The HDglass filament comes in an impressive 32 color options, in both 1.75 mm and 2.85 mm diameters and several spool sizes, allowing you to buy the basic colors in bulk (up to 8 kg for black, white, and grays). There’s another 13 color options for ReForm rPET, which sells for just ~$20 per kg.

FormFutura HDglass

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Prusa Research

If you’re after a filament with an exceptional tolerance or large color selection, Prusament PETG may be worth a look. Being a fan favorite, there’s lots of support online if you run into any issues while printing.

Prusament PETG is avalible in over 20 color options, including clear, matte and glossy black, “ocean blue”, and “lipstick red”, among others. There’s also the carbon-infused PETG for extra strength and durability. Keep in mind they only manufacture 1.75 mm diameter filaments.

Prusament PETG

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