Maintenance and conservation of resins

Maintenance and conservation of resins

Within 3D printing materials, resins are a particular case in point. While filaments and powders are based on thermoplastic materials intended to be formed by heat (either extrusion or sintering), resins are based on a reactive liquid mixture of oligomers, crosslinking agent and initiators.

This difference is particularly important, as stimuli such as light, temperature and oxygen can initiate and promote the polymerisation reaction. This means not only that resin requires better preservation than filaments, but also that it has a shelf life.

In the presence of light, the oligomers present in the resin begin to bond together in a process known as polymerisation. When enough oligomers are bound together, the resin becomes solid, however, until it solidifies, the resin becomes increasingly viscous.

Effect of light on resins

3D printing resins include photoinitiators, molecules that, in the presence of light, initiate the polymerisation reaction causing the oligomers to bind to each other. Although the initiators used are particularly sensitive to blue and UV light (405 nm, 385 nm and 365 nm), this does not mean that they cannot be activated by other types of light, they simply react more slowly.

Therefore, in order to keep the resins in the best possible condition, they should be protected from all types of light. It is advisable to remove the resin from the tray when not printing and store it in the container provided by the manufacturer. Most resin 3D printers include an amber or red cover to protect the interior from blue light.

Resin tank

Image 1: Resin tank. Source: FormLabs.

Although this is an effective solution to protect the resin for short periods of time, it does not prevent degradation in the medium to long term. Some printers include interchangeable tanks with lids to store the resin, however this solution is only recommended if a new print will be made within a short period of time.

Heat effect

Although temperature does not have as much influence as light, and generally does not generate spontaneous polymerisation, it does affect reactivity. Generally, the polymerisation reaction is favoured in the presence of high temperatures, causing it to occur faster. It is advisable to always store resins at temperatures below 20 ºC, the optimum temperature being between 10 ºC and 15 ºC.

For this reason, it is always advisable to print at temperatures above 20°C.

Effect of moisture on resins

Something that is not usually considered when working with resins is the influence of humidity. The first acrylic resins for 3D printing had a low hygroscopicity, so humidity was not a problem, however the appearance of new technical resins, some with a greater capacity to absorb water such as ABS or Tough, makes it advisable to store these resins in environments with low humidity.

Moisture in a resin generally has no visible effect on parts and is not usually the cause of printing failure, but it can alter the final mechanical properties of the part.

Resin recovery after an impression

During printing, the resin in the tank partially degrades due to light leakage and the heat generated by the light source. This generally causes an increase in the viscosity of the resin, as well as the appearance of solid residues and impurities.

Resin filter

Image 2: Resin filter. Source: Filament2Print.

To recover the resin and prolong its life, it should be filtered after each print to remove solid residues and impurities. It is also advisable to mix it with new resin before the next print to reduce its viscosity and improve its reactivity.

Resins with biocompatibility certification

Resins with a biocompatibility certificate require special preservation, because, in addition to ensuring their good preservation, contamination with other resins or impurities must be avoided in order to guarantee their certification. For this purpose, the following recommendations must be followed:

  • It is very important to handle resins in an aseptic environment and always wear gloves and a mask.
  • It is essential to always use separate tanks and platforms for each resin. If this is not possible, the 3D printer should only be used with materials that have the same degree of biocompatibility.
  • If other accessories or tools are used, such as filters or spatulas, one per resin type or disposable tools should be used.
  • For filtration, the use of fibre-based filters (paper, fabric, PP, etc.) should always be avoided due to the risk of fibre detachment and contamination. Ideally, a stainless steel sieve or mesh of at least 200 mesh should be used.


It is common for resins to include a "best before" or "use by" date. This date is indicative and does not imply that a resin cannot be used after this date, but it is the date until which the manufacturer can guarantee the good condition of the resin if the container has not been opened.

Once the resin container has been opened, this date is no longer important, as its useful life will depend on its use and proper conservation.

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