The resin or the room is too cold

Symptom

In the cold (in winter or in an unheated room) prints fail more often: parts do not stick, layers separate or parts come out incomplete, and the resin feels thick. Some printers warn that the ambient temperature is low.

Likely causes, from most to least likely

1. The room is below the recommended working temperature.
2. The resin comes from a cold place: it is thicker, flows worse and cures worse.
3. The exposure has not been adjusted for the cold, which changes the time the resin needs.
4. The temperature rises and falls during the print.
5. The resin has not been shaken and its components have separated.

Checks to tell which one it is

• Measure the temperature next to the printer before and during the print.
• Check where the resin was stored and whether it feels thicker than usual.
• See whether the printer shows a low ambient temperature warning.

Before you start

Uncured resin irritates skin and eyes: wear nitrile gloves and safety glasses, ventilate the room and do not look at the UV light. Before taking anything apart or cleaning it, switch the printer off and unplug it, unless a step says otherwise. If in any doubt, stop and ask a professional.

Step-by-step fix

1. Print somewhere warm

   Put the printer in a stable indoor room, never outdoors. As a starting point, Phrozen considers 24 to 30 °C ideal and advises against printing below 18 °C; Prusa asks for the environment not to drop below 16 °C.

   Check: The thermometer next to the printer shows a stable reading within that range.

   If that does not fix it: Warm the resin and adjust the exposure.

2. Warm and shake the resin

   Let the resin reach room temperature before using it: Prusa recommends keeping it between 18 and 32 °C because cold changes its viscosity. Shake the bottle well with the cap closed (Prusa says about 10 seconds). If it froze, Formlabs says to thaw it and shake it well before use.

   Check: The resin flows normally and has an even colour.

   If that does not fix it: Adjust the exposure.

3. Adjust the exposure for the cold

   If you cannot reach the ideal temperature, increase the exposure: as a guide, Phrozen suggests 20% more between 18 and 24 °C. Confirm it with an exposure test.

   Check: Parts stick and come out complete.

   If that does not fix it: Stabilise the temperature.

4. Keep the temperature stable

   Avoid the temperature rising and falling during the print. If you cannot heat the room, Phrozen suggests fitting a heater to the printer that keeps a constant temperature.

   Check: The temperature stays stable from start to finish.

   If that does not fix it: Check the levelling and the bottom layer exposure (print not sticking to the build plate sheet).

Prevention

• Store the resin tightly closed, in the dark and at the temperature its manufacturer gives (Formlabs, for example, 10 to 25 °C).
• Check the temperature before starting long prints.
• Always shake the resin before use.

Still not fixed?

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Printers it applies to

Any resin (MSLA/SLA) 3D printer, from any brand.

Official sources

This guide summarises the official documentation linked here:

• What is the Optimal Temperature for 3D Printing? · Phrozen
• Resins · Prusa Research
• Ambient temperature too cold #10703 (SL1/SL1S) · Prusa Research
• Resin care · Formlabs