Should You Print PETG on Glass Surfaces? (Solved!)

The strength of the adhesion between the first layer of the model and the build plate is one of the primary factors that decide how successful your 3D printed model will turn out, as the model needs a foundation to rest upon during the 3D printing process.

The vital point to consider here is both a too-low bed adhesion strength and a too-high bed adhesion strength are unfavorable for the print’s health, with the former causing issues such as warping – and the latter making it impossible to get the model off the bed.

Today, our topic will be the relationship between PETG and glass, where we will analyze if a glass bed is an optimal surface for PETG that doesn’t bring any adverse effects related to the strength of the bed adhesion.

So, should you print PETG on glass surfaces?

As PETG sticks way too firmly to glass surfaces, to the point where it’s possible to both damage the object and the build plate while trying to separate the model from the bed, we don’t recommend printing PETG directly on glass.

On the other hand, it’s possible to make glass surfaces suitable for printing PETG by applying a separating agent, such as hair spray, which will form a layer on the glass surface and prevent the plastic from sticking too firmly.

In the upcoming sections, we will dive deeper into whether it’s a good idea or not to print PETG on glass surfaces, discuss the optimal ways to conduct the printing process and answer some frequently asked questions related to printing PETG on glass.

Should You Print PETG on Glass Surfaces?

There is no denying that glass beds are pretty widespread, with most 3D printers shipping with one, and while the combination of PLA and glass works just fine, the situation is slightly different when it comes to PETG.

We highly recommend against printing PETG directly on a glass surface, as the strength of the adhesion between PETG and glass is way too sturdy. While this may sound like a good thing at first, as the bonds between the first layer of the model and the bed need to be strong, too much adhesion can also be harmful.

In a nutshell, when the adhesion strength between the build plate and the object is too much, removing the model from the surface without damage will become pretty challenging and often end up with the scratching of the glass and the bottom layers of the model separating from the rest.

As the aim should be to achieve a balanced level of adhesion between the object and the build plate, refraining from printing PETG directly on glass is a good idea to avoid issues down the line.

Fortunately, this doesn’t mean that there is no way to prepare glass surfaces where they would be suitable to print PETG, which will be the topic of our upcoming section.

How to Print PETG Successfully on Glass Surfaces?

Even though PETG inherently sticks very firmly to glass surfaces, which is definitely something we can’t ignore, there are indeed ways to print PETG successfully on glass with the correct precautions.

Our primary recommendation to print PETG successfully on glass surfaces, without getting the objects stuck to the build surface, is to apply a separating agent, such as Windex or hair spray, on the build plate before starting the printing process.

You can either spray the separating agent directly on the build plate or spray a microfiber cloth with it and gently wipe the build plate and spread the separating agent around.

The separating agent will then create a thin layer on the build plate, which will allow you to easily pull the PETG off the glass once the print is over.

Assuming that you have the essentials down, such as configuring the print settings correctly, leveling the bed, and ensuring that the build surface is clean, this process should allow you to print PETG on glass without any issues.

Does PETG Stick to Glass?

As both different filament types and different build surfaces have distinct properties of their own, it’s only normal not to have an idea of whether PETG would stick to glass or not if you have no prior experience with this combination.

PETG does indeed stick to glass, and in fact, to a fault, considering how strongly PETG sticks to glass makes it almost impossible to remove it from the glass without causing damage.

As a result, the thing to be aware of while printing PETG on glass is not the fact that you may end up with weak bed adhesion, but the exact opposite, where you may not be able to get your object off the build plate.

How Do You Get PETG Off a Glass Bed?

Due to PETG sticking tightly to glass surfaces, getting it off your printer’s glass bed can be quite a chore, especially if you have no idea where to start.

Here are some of the things we recommend trying to get PETG off a glass bed:

  • Place the glass bed (and the model) into the freezer for 10-15 minutes at a time, and repeat until you see results. This process should cause the PETG to pop off the glass bed as cleanly as possible due to the contraction that occurs in the low temperatures of the freezer. While using this method, it’s vital that the model and the bed have cooled down to room temperature and that you don’t leave them in the freezer for too long without observing the effects.
  • Fill a waterproof plastic bag with ice, and place it on the glass bed around the model. This method is an alternative to the freezer method mentioned above, which can come in handy if you can’t fit the glass bed in your freezer. Once again, it’s vital that you wait until the model and the bed has cooled down to room temperature before applying the ice.
  • Heat the bed to its standard temperatures, and spray small amounts of isopropyl alcohol around the model. When the alcohol evaporates around the model due to the heat of the bed, it will make its way into the space between the model and the bed and make it easier to pry the PETG off the glass by weakening the strength of the adhesion.

Ensure that you do not try to directly pry the PETG off the glass bed with a sharp tool, as you will most likely end up scratching or even breaking the bed depending on the amount of force you use.

PETG Not Sticking to Glass – What to Do?

While PETG is known to stick rigidly to glass, there are cases where the complete opposite happens, and bed adhesion issues between PETG and glass start showing up.

In the rare cases where PETG does not stick to glass, here are the things we recommend trying:

  • Ensure that parameters with direct impact (such as nozzle temperature, bed temperature, cooling fan speed) on bed adhesion are correct.
  • Re-configure the first layer settings as optimally as possible.
  • Level the print bed, preferably with an auto bed leveling sensor for consistency.
  • Clean the print bed thoroughly with rubbing alcohol.
  • Use an adhesive such as hair spray or glue stick on the build plate.
  • Add brims and rafts to your model.

As PETG is inherently supposed to stick to glass very firmly, bed adhesion issues between PETG and glass often point towards problems with the printing process, with the most common ones being a bed that isn’t level and a build plate that isn’t clean.

Wrapping Up

While the combination of glass and PETG isn’t the most optimal, you should be able to print PETG on glass without any issues if you prepare the surface before the printing process and make it suitable to accommodate PETG.

To quickly recap, we recommend refraining from printing PETG directly on a glass surface – as PETG will end up sticking to the glass way too firmly and become quite challenging to remove without causing damage to either the object or the build plate.

On the other hand, with the correct preparation, such as applying a separating agent to the glass surface before printing PETG on it, you can reduce the strength of the adhesion to a level where it will be more suitable for 3D printing.

Happy printing!