How Well Do 3D-Printed Objects Float?

The relationship between plastic and heat and water is an important consideration when designing or prototyping. 

For example, when designing plastic parts that might be used as part of an engine, heat will play a part in determining what material and settings to use to print that part. If you were designing something like a fish float, you would want to know what materials and settings will make it buoyant.  

This second example brings us to the subject of this article. Can 3D-printed items float? What type of materials and settings do you use to make items that can float? If you own an aquarium, and you want to know how to 3D print items you can safely use, then this article will be especially useful to you.

Does 3D Print Plastic Float?

The ability of a material to float is partly determined by its density or how heavy it is relative to how big it is (mass multiplied by its volume). For a material to float it must be less dense than the substance it is placed on. Water, for example, has a density of 1 g/cm3 (1 gram per cubic centimeter). Most filaments are denser than water (they have a density greater than 1 g/cm3) so will not float in water.

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The first step to printing something that will float is picking the right filament. Certain types of filament will float better due to their lower density. Some like metal filament will obviously present more of a challenge due to their higher density.

ABS1.04 g/cm3
FLEXIBLE1.19 – 1.23 g/cm3
PLA1.24 g/cm3
HIPS1.03 – 1.04 g/cm3
PETG1.23 g/cm3
NYLON1.06 – 1.14 g/cm3
ASA1.07 g/cm3
METAL FILLED2 – 4 g/cm3
WOOD FILLED1.15 – 1.25 g/cm3
PVA1.23 g/cm3
3D Filaments Density


Does PLA Sink Or Float? 

Polypropylene is the only filament with a density lower than water (0.9 g/cm3). This makes it the only filament that will naturally float in water. PLA has a specific density of 1.24 g/cm3. For a material to float in water it should have a density of less than 1 g/cm3 so PLA will sink because it is denser than water. 

Does this mean only items printed from polypropylene will float whereas objects made from PLA or ABS will sink? Not necessarily because there is more to making a 3D-printed item float than just the material it is made from.

Do 3D Printed Items Float?

3D printing filament will likely sink. However, the buoyancy of a 3D-printed item is determined mostly by the specifics of its design and not just the material it is made of. There are two main factors that would affect the buoyancy of a 3D-printed item. These are the infill density and shell thickness. 

Infill Density

Infill density is a measure of how hollow or “filled” a 3D print is. It is set as a percentage. The higher you set it, the more filled your print will be. A print with a fill density set to 100% is solid. An item that is solid is denser so is highly likely to sink. 

Naturally, setting a lower fill density makes the print hollow. A print with a fill density set to 10% is almost completely hollow so will likely float.

Shell thickness

Infill density controls the inside of a print. Shell thickness on the other hand sets the thickness of the outer layers of a print. Printing thinner walls reduces the density of your print just like lowering the infill density. This should improve the ability of the print to float.

Can 3D Printed Objects Go In Fish Tanks?

3D-printed items can be used in fish tanks although not all materials are suitable. 3D-printed items made from metal for example can leach poison as they degrade. PLA, PETG, and ABS are the safest materials for use in an aquarium. 

3D printing is a great way to create fixtures and decorations for an aquarium without breaking the bank. 

Can ABS Be Used For Aquariums? 

ABS is the raw material used for most plastic fixtures like the pump casings and brackets used in aquariums. 

Not all ABS filament is the same, however. Some brands of ABS have been known to leach chemicals into aquariums and poison the fish. To avoid this happening to you, be selective about which ABS you use. 

You want to avoid filament that might contain additives like dyes for example. The dyes used to give filament a particular color will likely leach toxin into the water. It is for this reason that pure white or black filament is recommended for aquarium use. Source

Can PLA Be Used For Aquariums?

PLA offers a few characteristics that make it an aquarium-safe alternative to ABS. It is made mostly from organic material so there is less chance of it leaching harmful toxins into the water. With that said PLA is not as water-resistant as ABS and breaks down much faster, especially in saltwater.

What Happens If A 3D Print Gets Wet?

Most filaments are water-resistant. While they may soften and weaken when they come into contact with water, this typically happens over a year or more of repeated exposure. PVA, however, is water soluble. This is why it is used as a support for PLA or ABS prints. 

Supports are an essential part of a 3D print. They are used for supporting prints that have overhangs or bridges. While supports are almost indispensable in prints with irregular shapes, they are notorious for being difficult to remove from a print. 

PVA solves the problem of hard-to-remove supports as it dissolves in water. Rather than spend hours trying to remove or cut away PLA or ABS supports, PVA simply melts away when immersed in water.

How Sturdy Are 3D Printed Objects?

The strength of a 3D printed part is determined firstly by the printing technology. Resin printing is said to produce stronger parts compared to FDM printing. The second factor to consider is the material. Carbon fiber filament will produce stronger prints than PLA for example.

Resin printing is said to produce sturdier prints because it is isotropic. This means the prints have uniform strength across the vertical, horizontal, or diagonal plane. FDM prints are anisotropic which means strength is highly dependent on the direction of the build.


I am a very well experienced techie civil engineer who's extensively interested in 3D printing technology and even more captivated by the potential of 3D printing livable structures

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