Mushrooms & More

Filter bags by Unicorn

 ECO Consult distributes Unicorn bags in Europe. Unicorn bags are used all over the world by spawn producers and mushroom growers. Normally 5 types of bags are in stock, other types of bags will have a longer delivery time as they have to be sent over the ocean.

The bags differ in gas exchange: #14 has a lower gas exchange than 3T and the BN type of filter is very open. It depends on growing techniques, amount of supplementation and temperature ranges which bag is most suitable. Many shiitake growers use 3T, and many spawn producers use 14#. However, the opposite choice has proved OK for both spawn producers and mushroom growers. You can order samples to test which bag suits your needs best.

Advantages Unicorn bags

  • stay soft and easy to seal after heat treatment in autoclave for six hours at 262 F (125 C).
  • can be any size and length, with as many filters as you want, where you need them.
  • can provide gas exchange, but exclude water vapor, so your spawn does not dehydrate.
  • provide a perfect environment for fungi growth. Because we produce our own filters, gas transmission rates can be adjusted to suit your needs.
  • can be used for fungi, nematode production for bio-control of insects.

UNICORN provides free development to create a microvented bag for your application, when more than 50.000 bags are ordered at a time. Please contact us if you need custom designed bags.

Growers can choose between a number of different types of bags and even bottles. The best choice for their situation depends on several factors: local availability, sterilization method, gas exchange, price, melting point, size, brittleness and transparency.

The sterilization method in particular determines the choice of the plastic bag material:

Sterilization method
Plastic type
Sterilization of substrate in bags by steam, high pressure (121 °C)
(laminated) PP
Sterilization of substrate in bags by steam, low pressure (96 - 98 °C)
Sterilization of substrate in bags by gamma radiation
Bulk sterilization and spawning
Pasteurisation at ca. 60 °C
PE, laminated PE/PP
Preheated substrate or chemical sterilization


The general term “plastic bags” can be better specified in two grades of polyolefin, polyethylene (PE) and polypropylene (PP). These two materials are still the least expensive, and the most produced in the world. Cost of PE and PP are about the same, but this may vary depending on the current market situation. PE has a low melting point, and PP has a higher melting point. In general PE starts to melt at temperatures above 90 °C, and PP can withstand up to 130 °C. PP disintegrates when sterilized by gamma irradiation. Thus laminated bags of PE/PP can not be used for irradiation, nor for high temperature sterilisation, but only for pasteurisation at low temperatures.

A variation of PE is HDPE, or high density polyethylene. This material has a higher melting point than regular PE and can withstand up to 108 degrees °C , but it has the disadvantage of having a heavy haze and is much less transparent than PE, as well as being more brittle. Therefore most growers dislike using this material, as contamination is not easily detected.

In general PP is more brittle than PE, but by adding plasticizers in small percentages, PP can be made soft and will not crack at side folds, gussets and low temperatures. As PP has a higher melting temperature than PE, the sealing temperature is also higher. Laminated bags of low temperature melting point PP and high temperature melting point PP reduce chances of breakage due to stress; the high temperature PP is normally at the outside of the bag.
Another consideration when choosing bags, is how the proper gas exchange can be achieved. Several strategies are currently employed:

  • bags without filters, gas exchange through cotton of foam plugs,
  • bags without filter, with some (limited) air exchange through the plastic, the spawned part is covered with a paper tape and the bags are cut open when the mycelium colonised part of the substrate,
  • gas exchange through filters on top of the plastic (e.g. Unicorn),

The third consideration is the form of the bag and the volume. The amount of substrate to be filled in each container has increased during the years. The plastic bags used to be rather small, containing 0.5 to 1,25 kg of substrate per bag. Nowadays up to 15 kg of substrate can be filled per bag, thus reducing labour. The substrate has to be rather loose then, otherwise aeration will still be insufficient. A disadvantage of larger amounts is that the internal heat can rise too high for the mycelium; cooling becomes necessary then, especially when the substrate is spawned through as is the case in bulk sterilization and when farmers shake the spawned bags for faster spawn run. Yet another disadvantage is that the form may be less optimal; for shiitake, longer cylindrical bags seem to produce better than the same weight of substrate closely packed together.