The Best Way to Store Liquid Screen Printing Emulsion & Capillary Film
It is best practice for screen printers to keep extra screen printing supplies key items on the shelf, such as screen printing emulsion. This ensures they can keep coating, burning and making screens. Many screen printing supply companies provide a discount if you buy in bulk and give a better price for buying a gallon versus a quart. However, all screen printers must balance keeping enough in inventory and keeping enough so that their current supply does not go bad.
Storing Photopolymer Emulsions: Be Aware of Temperature & Time
Unopened photopolymer emulsions (SBQ) can last a couple years if stored properly. The main factor in proper storage is temperature. When it gets too cold, emulsion can freeze. This is why you see “freeze warnings” from emulsion manufacturers like Ulano and Lawson. Any reputable screen printing supply company will not ship you emulsion that will sit in a delivery truck during freezing weather. This is because when the emulsion arrives to your shop, it will have gone bad. The key to avoiding this is to plan ahead in winter months.
Photopolymer can also get too hot during storage, causing the photosensitive chemicals to react poorly. Emulsion is most stable when stored at room temperature (somewhere in the mid 60’s to the upper 70’s degrees fahrenheit). If you are going to store liquid emulsion for a while, placing it in a refrigerator can work but just make sure it does not freeze.
Aside from the temperature, the time it sits undisturbed has an effect. When liquid emulsion sits on the shelf the solids fall out of suspension and settle to the bottom of the container. If you have ever stirred emulsion that has been sitting for a while, you will notice all the particles at the bottom and the liquid on top. While not necessarily a problem, it does mean you have to vigorously stir the emulsion for several minutes prior to use. Your goal is to evenly distribute the solids back into the liquid. After stirring, make sure to let all the air settle out before use.
Lastly, liquid emulsions run a risk of developing mold and mildew. Quality emulsion brands like Ulano and Lawson include a fungicide to combat this possible problem. Double check for any visible growths or strange smells when you open the container if you use a “bargain” brand.
Storing Dual-Cure Liquid Emulsion
Dual-cure emulsions require screen printers to mix in the diazo sensitizer prior to use. Prior to adding the diazo, unsensitized dual-cure emulsion has a shelf life similar to the Photopolymer SBQ emulsion (described above). Adding the diazo shorts the shelf life to about 4 - 6 weeks. You can store dual-cure in similar temperature settings as photopolymer emulsion.
Storing Capillary Film
Capillary film is another form of emulsion, but because it is already in a solid state (not liquid), some of the issues that come with liquid emulsions are avoidable. Capillary film tends to have a longer shelf life and is not prone to freezing. This type of emulsion may last a couple of years when stored in ideal conditions of between 40-86℉ and at a relative humidity of 45-60 and without direct exposure to light.
For Direct Emulsion Problems and Solutions check our Direct Emulsion Troubleshooting Checklist
Whatever type of emulsion you prefer, keep in mind the storage requirements and always follow the safety data sheet (SDS) and any storage instructions it comes with on how to keep it safe and effective for as long as possible. For help finding an emulsion to fit your needs, read our article Which Photo Emulsion Should I Use for Screen Printing?