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Can Resin 3D Prints Hold Water?

Technology of liquid photopolymerization under UV light

Resins-based 3D printing is often used for prototyping and creating ornamental or decorative pieces. These use photosensitive resins that harden when exposed to different wavelengths of light. These resins are manufactured to meet diverse requirements and have various properties and different sensitivities to distinct operating conditions.

What are 3D printing resins and how strong are they?

While common industrial plastics like ABS and polycarbonate (PC) can be used in FDM 3D printing, resin 3D printers need unique photopolymer resins that harden (cure) under UV light. Epoxy- or acrylate-based resins are the most common types used in 3D printing, with the latter type being more frequently utilized in desktop printers. Many people believe that resin 3D printed objects are delicate and more suited for decorative and prototyping uses than for functional and load-bearing ones. However, this is only the case if the resin is improperly chosen.

However, using a generic resin for a difficult task won’t result in the expected strength. A wide range of businesses uses super-strong resin in various ways. Castable resins are used to create jewelry, while 3D printing in dentistry develops surgical guides, crowns, and mouthguards. High-temperature resins may also create rubber-like components suited for various industrial applications. The toughness of the resin does not guarantee that prints made with it will be twice as durable as prints made with regular resin. The strength of the final print is significantly influenced by additional variables like model design and print settings. However, it is simple to tell which material is stronger by comparing tensile strengths.

What are resin-based 3D printers commonly used for?

Resin-based 3D printing is generally known as vat polymerization. Liquid resin is selectively hardened by UV light while it sits in a vat during vat polymerization. In this instance, there is no material deposition. Vat polymerization is most frequently used in the dental and medical fields. For example, in producing microneedles, dental and other prostheses, surgical practice tools, and hearing aids. Interestingly, the development of small living tissue structures using this method has been published in a 2021 study evaluation of vat photopolymerization technology, highlighting numerous applications of vat polymerization thus far.

Can resin prints hold water?

The question is whether closed 3D structures made using vat polymerization prevent water from entering or exiting them. There is no black-and-white answer to this question, as it depends on multiple factors. As the resins in their liquid form are susceptible to loss of function when exposed to moisture, it is necessary to convert these resins to a form that cannot be affected by humidity. An extended period of UV light exposure is required to cure a resin 3D print. The photopolymer resin undergoes a chemical shift during this period when the UV light or other curing agents acts to harden it, simultaneously giving the structure a smooth surface. Making resin 3D printing waterproof is possible. When the liquid photopolymers are hardened and cured, they become waterproof, but for the print to be watertight and to hold water, there must be no fissures, holes, or gaps. Additionally, 3D images made from cured resin won’t absorb water, making them ideal for multiple uses.

However, over-curing or exposing the print to UV light or other curing agents for too long makes it brittle, increasing the risk of cracks and fissures that could allow water to enter the structure or leak out from it without control.

 Technology of liquid photopolymerization under UV light

How do resin-based 3D Printed samples hold water?

Now that it has been established that resin-based 3D printing samples are waterproof when cured, it is necessary to understand what steps are required to make these prints waterproof and watertight. These steps involve measures ranging from curing to modifications in printing parameters as well as design parameters.

Choosing the right material

First and foremost, selecting the appropriate material is crucial. Resin that can be “water-washed” will have greater waterproofing capabilities. Since one can use water to clean the finished prints with this kind of resin, it is also considerably simpler. Resin that is water-washable is more water-resistant and won’t deform when wet. The finished print must be waterproof, but it might not be watertight; therefore, further procedures are needed. Additionally, it is essential to avoid wetting resin 3D printing until they have thoroughly dried off. Rinsing or testing the water resistance of a brand-new 3D resin print is not acceptable; ultrasonic cleaning and UV curing are recommended.


Resin printing is a quick and simple procedure that may be completed in a short amount of time. Resin prints have a stronger composition when the finish is more constant throughout the curing process. Additionally, robust and aesthetically pleasing goods are produced through the curing phase. However, over-curing occurs due to the high heat that perfects the curing process, making the print readily fragile. Sunlight also heats it up in addition to the heat and UV radiation utilized in the curing process. Curing is sped up by the quick cooling of newly hardened 3D resin. As a result, the subsequent layer of liquid photo-polymerizing resin may not be able to adhere precisely to the hardened portion. However, inside a very heated enclosure, you cannot have a particularly slow hardening or curing process. Unhardened resin warps when it is dipped in the vat or tank for the following layer due to delayed curing. Cracks, flaws, and gaps result from warping, layer movement, or structural imperfections. Such irregularities may compromise the 3D-printed resin model’s water tightness.

Constructing higher and thicker layers

If the goal is to make a waterproof and watertight object, it is within reason to give it higher layers. There wouldn’t be any gaps since when resin layers are made higher and thicker, there is no room between them.

Designing walls that are solid and strong

It goes without saying that sturdy walls are necessary for a resin 3D print to be watertight. However, the shells or walls must also be substantial or sturdy. The walls of the 3D-printed resin model must be robust to endure pressure if it is intended to make it hold water, float, or be immersed. Therefore, weak walls are an impossibility. Additionally, bespoke infill options are available based on the design and intended use of the object. For instance, a relatively hollow infill is needed to make the object buoyant. A 3D-printed resin model with enough air pockets inside of it can float on water. A solid item might not become buoyant with 100% filling.

Additional resin coating

Finally, treating the object with epoxy resin is advised before fully curing it. Any minor holes in the material will be filled in with a clear coat. Users must always wear protective gloves when handling an uncured print for safety. It is merely a matter of painting it with transparent epoxy resin. The pattern is also smoothed out during this process, giving it a more polished appearance.

Testing out water holding capacity

Testing the print is crucial when curing is complete. Fortunately, this step is simple. Simply immerse the print for a few hours in the water or allow it to float if the model is buoyant. Check the print after being submerged in water for cracks and water buildup. The item is watertight if there are no visible signs of deterioration or water leaks. If there are cracks, the design must be adjusted. If the print didn’t come out perfectly the first time, that’s okay. Users can experiment with other 3D resins or modify the slicer software’s programs. Additionally, pay closer attention to the transparent epoxy resin’s waterproof seal on the print.

Are resin-based 3D models safe for holding drinking water?

Although resin-based 3D printed models are watertight when appropriately cured and designed to prevent cracks and hold water, resins are unsafe for storing drinking water or other potable liquids. However, food-safe coatings are being developed that could eventually allow resin-based 3D models to be food safe.

Which is the Best Software for Creating 3D Models?

When it comes to creating 3D models, there are many different software options available. Some are more user-friendly than others, while others offer a wide range of features and functions. For many designers and artists, the best software for creating 3D models is SelfCAD. With SelfCAD, users have access to an intuitive modeling interface that makes it easy to create complex 3D shapes and forms. It’s one of the best alternatives to Vectary. In addition, SelfCAD offers a robust library of tools and effects, allowing users to add textures, lighting, and motion in an intuitive way. Whether you are looking for powerful modeling capabilities or sophisticated rendering functions, SelfCAD is the clear choice for creating stunning 3D models.


In conclusion, Resin-based 3D prints are waterproof only after curing is properly carried out. Curing only makes it waterproof; in order to make a 3D structure hold water or to make it watertight, several other steps need to be taken. The material chosen should have waterproof properties, and the design should have thick and high walls. It is also vital to ensure that the design has strong walls without gaps or cracks. Curing is critical to make the structure hold water; proper curing not only makes it hard enough but also gives the print a smooth surface that does not have cracks. Over-curing might cause the structure to be brittle and prone to cracking. Quick curing also negatively affects the print’s structural integrity, thereby affecting the water-holding capacity. These prints could also be coated with an additional layer of resin to give them a final waterproof coating after the curing process. It is also essential to check for leaks after curing.