Propolis Screens and Collection

A propolis trap (propolis screen, propolis collection mat) is a perforated or slotted sheet used to collect clean propolis in the hive by exploiting the bees' instinct to seal narrow gaps with propolis. The trap is usually placed under the crown board; when full it is frozen and flexed so the propolis falls off. Correct timing and keeping well away from treatment periods are the two conditions for a quality product.

How does a propolis trap work?

Bees seal with propolis any gaps in the hive that let in light, air or cold and are too narrow for them to pass through. The trap moves this behaviour onto a surface of the beekeeper's choosing: to the bees, the many narrow gaps in the sheet placed in the hive are "openings that need sealing". As the bees fill the gaps, propolis builds up on a surface that is easy to strip.

Unlike propolis collected by scraping, trap propolis contains no wood shavings, paint or dust, and its wax content is lower. That makes it the most suitable raw material for processing and sale.

Types of propolis trap

• Plastic screen (mat): A flexible plastic sheet with fine gaps; the most common type. Thanks to its flexibility, frozen propolis falls off easily when it is bent.
• Slotted board: Boards with long slots a few millimetres wide; they work on the same principle.
• Side-wall traps: Panels with narrow slats or slots fitted to the hive wall or the edge of a box; used with some hive types.
• Wire mesh: Metal mesh can also be used, but it is hard to bend and clean; propolis sticks more firmly to metal.

Whatever type you choose, the sheet must be made of food-grade material, easy to clean and the right size for the hive.

Where and how do you fit a propolis trap?

1. Position: The screen usually goes in the top box, on top of the frames' top bars and under the crown board.
2. Light and air: To encourage the bees to seal it, the crown board is raised slightly or a small gap is left above the screen. The hive roof must stay closed so that rain cannot get in.
3. Bee space: There must be room between the screen and the top bars for bees to move; otherwise they may build wax under the screen.
4. Checking: Check the screen every few weeks; if most gaps are filled, remove it and fit a clean one if needed.

When should a propolis trap be fitted?

The most productive period is late summer and autumn, when the bees are preparing for winter and sealing gaps. In spring and during a heavy nectar flow the bees spend their energy on honey and brood; propolis builds up slowly.

• Remove before treatment: If varroa or any other treatment is to be applied, take the screen out of the hive before treating. Fat-soluble active ingredients accumulate in propolis.
• Don't leave it over winter: In cold regions an open-gapped screen at the top can cause heat loss during wintering; remove it before winter and close the hive normally.
• Choose strong colonies: Weak colonies fill the screen slowly and lose heat through the top.

How do you get propolis off the trap? Step by step

1. Remove the screen: Take the full screen out of the hive; gently shake or brush off the bees.
2. Bag it: Put the screen in a clean food bag; this keeps out dust and foreign matter and catches any falling pieces.
3. Freeze it: Leave the screen in the freezer for a few hours or overnight. In the cold, propolis hardens and becomes brittle.
4. Flex and rub: Bend, twist or rub the frozen screen by hand inside the bag; the propolis flakes off. Remove stuck pieces with a plastic scraper while still frozen.
5. Clean it: Pick out bee parts, lumps of wax and foreign matter.
6. Pack it: While still cold, put the propolis in an airtight, dark container and label it.

When is propolis collected by scraping?

Even in hives without a trap, propolis can be scraped from the frame lugs and box edges at every inspection. This is done both to make frames easier to lift out and to accumulate small quantities. Scraped propolis is dirtier, however; propolis scraped from painted surfaces may contain paint and preservatives, so keep it separate and never mix it into food-grade batches.

Cleaning and caring for the trap

• Remove residue by freezing: The thin layer left on the screen is removed at each harvest by freezing and rubbing it again.
• Don't wash in hot water: Propolis turns sticky in heat and spreads into the gaps; if necessary, rinse in cold water and dry.
• Store dry: Keep cleaned screens flat in a dry place out of the sun; a warped screen will not sit properly in the hive.
• Disease: Never use the screen from a diseased hive in another hive.

Common mistakes

• Leaving the screen in the hive during treatment: The whole batch ends up with residues.
• Forgetting the screen in the hive over winter: Leads to heat loss and condensation.
• Mixing scraped and screen propolis: Lowers the quality of the clean batch.
• Not leaving a bee space: Bees fill the underside of the screen with wax, and wax gets into the product.
• Storing propolis warm and in the light: Volatile compounds are lost.

People who handle propolis regularly can develop contact allergy; wearing gloves during harvesting and cleaning is sensible.