The short answer
Keep spore syringes in the fridge at 2 to 8 C, cap on, out of the light, inside a sealed bag. Do not freeze them. Treated this way, a well-made syringe usually stays good for microscopy for 6 to 12 months, and often longer. Spore prints, kept dry and dark, last longer still.
The rest of this guide explains why each of those rules matters, how to spot a syringe that has gone bad, and how to handle prints, swabs, deliveries and labels.
Fridge at 2 to 8 C, never freeze
Spores are dormant cells. Cold slows down everything that could harm them: bacterial growth in the water, chemical breakdown of the spore wall, and the slow loss of viability that happens at room temperature. A domestic fridge runs at roughly 2 to 8 C, which is the range most vendors recommend. The door shelf is the warmest part of a fridge and swings in temperature every time you open it. Use a middle shelf towards the back instead.
Never put a spore syringe in the freezer. The water inside expands as it freezes. Ice crystals rupture the spore walls and can crack the barrel or push the plunger. A frozen and thawed syringe may still show spores on a slide, but many will be damaged, and the water often turns cloudy as bacteria take hold once it warms up.
If your fridge is shared with food, put the syringes in a labelled zip bag or a small plastic box. This keeps them away from condensation and from anyone who might mistake them for something else.
Keep the cap on and keep it dark
The luer cap is the only barrier between the sterile water inside and the air outside. Once you take the cap off to make a slide, wipe the tip with alcohol before you put the cap back on. Never store a syringe with a needle attached. The needle is an open path for contamination, and it is easy to stab yourself reaching into a fridge.
Light, especially ultraviolet light, degrades spores over time. A fridge is dark when the door is shut, so this is mostly a concern for syringes left on a windowsill or a bench. Keep them in their original packaging or in an opaque box.
Some vendors ship syringes with the plunger pulled back slightly so there is a small air gap. Leave it as it arrived. Do not push the air out, because that forces water through the tip and breaks the seal.
How long spore syringes last
There is no fixed expiry date for a spore syringe. Shelf life depends on how clean the vendor's process was, how fresh the print was when the syringe was made, and how the syringe was stored after it left the vendor. As a general rule:
- Fridge, cap on, dark: 6 to 12 months is typical, and many microscopists report usable slides well past a year.
- Room temperature: a few weeks to a few months before cloudiness becomes likely, especially in summer.
- Spore prints, dry and dark: commonly years. The spores are not sitting in water, so there is nothing for bacteria to grow in.
For microscopy, age matters less than you might think. Even an old spore keeps its shape, size and colour, so you can still measure and photograph it. What you want to avoid is a syringe full of bacterial growth that hides the spores under a fog of cells and debris.
Many Culture Cave vendors state when a syringe was made or when the batch was printed. Where they do not, ask. The guide on how to choose a spore vendor lists the questions worth sending before you order.
Signs of a bad syringe
Hold the syringe up to a window or a lamp and look through the barrel. A healthy syringe is clear water with dark specks or a thin dark layer at the bottom. These are the signs that something has gone wrong:
- Cloudiness. Uniform haze in the water, like weak milk, means bacteria. Clumps of spores are dark and settle. A bacterial cloud is pale and stays suspended.
- Floating growth. White or coloured strands, fluffy blobs or a skin on the surface of the water. This is mould or yeast and the syringe should be discarded.
- Off smell. If you push out a drop and it smells sour, sweet or rotten, bin it. Clean spore water has almost no smell.
- Colour change. Water that has turned yellow, green or pink.
- Plunger pushed out. Gas from microbial growth can slowly force the plunger back. If it has moved on its own, do not use the syringe.
A syringe with one of these signs is not dangerous to handle, but it is useless for clean microscopy and should not go anywhere near agar or liquid culture work with gourmet species.
Storing spore prints and swabs
A spore print is a dry deposit of spores on foil or paper. Keep it in its sealed bag, flat, in a cool dark drawer, or in the fridge inside a sealed container with a silica gel sachet. Moisture is the enemy of a print. If a print gets damp, mould will grow across the paper and the spores underneath are lost.
Swabs are sterile cotton tips rubbed across a fresh print, then sealed in a tube. Store them the same way as prints: dry, dark and cool. They carry fewer spores than a print but are very convenient for making a single slide. Our guide to spore prints and swabs covers how vendors make them and how to use them.
If you want a syringe from a print you already hold, make it fresh when you need it. A print kept dry for a year is usually in better shape than a syringe kept in water for the same time.
Transport and heat in the post
A parcel in a hot van or a sunlit letterbox can reach 40 C or more for hours. A day or two of that will not ruin spores outright, but it gives any bacteria in the water a head start. Good vendors pack syringes in padded or foil-lined mailers and ship early in the week, so parcels do not sit in a depot over the weekend.
When a parcel arrives, open it the same day and put the syringes straight in the fridge. If they arrive warm, let them cool in the fridge rather than the freezer. Do not use a syringe that arrived cloudy. Photograph it, contact the vendor through their storefront, and check the vendor's own returns terms. Culture Cave takes no commission, so your purchase and any replacement are handled directly with the vendor who sold it.
Buyers in hot climates, including our customers looking for mushroom spores in Australia, should favour vendors in their own country, where the parcel spends less time in transit. The shipping page explains how regions and delivery times are shown on each listing.
Labelling and dating
Every syringe should carry four facts: species or strain, vendor, date made or received, and the date you first opened it. Most arrive with a vendor label showing the first two. Add the dates yourself with a fine permanent marker on the barrel, because stick-on labels peel in a cold damp fridge.
Keep a simple log, on paper or in a spreadsheet, listing every syringe and print you hold. Note when you make a slide from each one and what you saw. Over time this tells you how long your own storage keeps syringes usable, which is far more useful than any general rule.
If you are unsure whether an old syringe is still worth a slide, the quickest test is to make one. The guide on how to use a spore syringe for microscopy shows what a clean sample looks like at 400x, so you can compare. And if you decide it is time to replace it, every spore syringe listing on Culture Cave shows the vendor's country, shipping regions and real reviews from other buyers.