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Liquid resins are photosensitive materials used for printing on DLP, SLA and MSLA 3D printers. Resins are also known as photopolymers and they are cured (solidified) by UV light - this also includes sunlight. Compared to filaments for FFF/FDM printers, the major difference is that there are not various materials such as PLA, PETG or ASA. There’s just THE resin; a base material that can be further enhanced with added colors or additives. The typical effects of additives would be increased hardness or toughness of the printed object.

Resins usually consist of three basic components:

• The core of the resin (monomers and oligomers)
• Photoinitiators - molecules reacting to UV light, which initiate the solidifying process
• Additives - admixtures that change the color and properties of the resin

Important information about resins

There’s a couple of things to keep in mind when working with resins:

• Wear gloves to avoid direct contact of the resin with your skin
• A simple respirator is recommended
• Keep out of the reach of children and pets
• Shake the bottle well before every use for around 10 seconds (make sure the lid is securely tightened before doing so)
• Wash with water and soap in case the resin gets in contact with skin/eyes
• If you experience itching or any kind of discomfort after skin contact, seek out medical assistance
• Keep away from light, store in opaque bottles
• Keep at room temperature (18°-32°C), lower temperature changes the viscosity of the resin
• Do not store in dusty areas
• Resin produces fumes - keep the room ventilated during printing
• Some people may be allergic to resins - in case you experience any kind of discomfort (itching, rash), stop using the machine and contact a doctor

Liquid resins should be treated as dangerous chemicals and you should follow your country’s laws regarding disposing of dangerous chemicals. There are usually special containers (e.g. oily waste cans) available for the public located near gas stations etc.

Which resins to buy?

Once you start looking for resins to purchase, always check the wavelength of the resin - it determines at which wavelength the solidifying process starts. The Original Prusa SL1 printer is calibrated for 405nm resins and has no brand restrictions. Since it’s an open-source machine, you can choose any brand of resin you like, as long as it is compatible with the 405nm wavelength. However, always use recommended exposure times for the resin of your choice - extremely incompatible times may even lead to your printer getting damaged (e.g. setting 30 second curing time for a resin that solidifies in 6 seconds).

Resins should be stored in their original containers and properly sealed, ideally in a dark room with a stable temperature. If the original container is damaged, use a non-transparent plastic bottle and the bundled funnel that came with the printer to pour the resin in it. Never store resin in bottles from drinks - if you have to, label it clearly. Do not store resins in cold places as it may lead to gelation of the resin.

Types of resins