Choose the Best Jars for Preserving Wet Specimens Long-Term

Proper preservation is essential for maintaining the integrity and longevity of wet specimens used for scientific study, education, and collecting. Selecting the right jar and storage method can mean the difference between a specimen lasting decades versus rapidly degrading.

With the growing demand for wet specimens, especially in educational settings, there have also been advancements in jar technology to accommodate this need. Some of the latest developments include jars with built-in temperature control systems, UV filtration, and even new materials like bioplastics and silicone that are more durable and sustainable than traditional glass.

Overview of Wet Specimen Preservation

Wet specimen preservation involves storing biological or anatomical samples in a fluid medium to prevent dehydration and decomposition. Examples of wet specimens include animal tissues, organs, embryos, and insects stored in formaldehyde, alcohol, or specialty fluids.

jars for wet specimens

Proper preservation allows detailed study and long-term storage of specimens that would otherwise rapidly degrade. However, the right jar and storage methods must be used to prevent evaporation of the fluid and contamination that can ruin the specimen.

When selecting a jar, key factors to consider are:

  • Ability to prevent evaporation for the duration of storage
  • Resistance to corrosion from preservatives like formaldehyde
  • Seals that remain airtight over decades
  • Inert materials that avoid contaminating the specimen

Types of Jars for Wet Specimens

Glass Jars

Glass is an optimal material for wet specimen jars because it is non-reactive, transparent for monitoring specimens, and available in a wide array of sizes and shapes. However, glass alone does not prevent fluid evaporation, so sealing options must be considered.

Glass with Plastic Inserts

Many wet specimen collections use glass jars with polyethylene or polypropylene inserts or liners. The inert plastic acts as a barrier against evaporation and prevents direct contact between the specimen and glass. Polypropylene lids screwed onto the glass rim over the insert complete the airtight seal.

These glass-plastic hybrid jars allow easy monitoring of specimens through the clear sides. The plastic inserts can be changed periodically if they become discolored from long-term preservative exposure.

Bail-Top/Cam-Lock Jars

All-glass bail-top jars and cam-lock jars provide excellent seals for wet specimen storage. Heavy wire bail mechanisms compress rubber gaskets against the glass lid, while cam-lock jars use industrial cam levers to lock the lid in place.

The rubber gaskets enable an airtight seal for containing fluids, but may require periodic replacement as gaskets can degrade over time with certain preservatives. Viton fluoroelastomer gaskets offer maximal chemical resistance.

Glass Crocks

Glass crocks are wide-mouth glass jars consisting of a vessel and lid sealed by a metal clamp. The clamp applies downward force, pressing the lid against a rubber gasket for an airtight seal. Glass crocks are excellent for large volume wet specimen storage.

The clarity of glass allows easy viewing of specimen integrity without opening the jar. Glass is impervious to chemicals and resists scratching compared to plastic.

Plastic Containers

Plastic containers and jars also offer reliable wet specimen storage, providing a lightweight and affordable option. Polypropylene and PET plastics are chemically inert enough for use with formaldehyde and alcohol.

Many styles utilize rubber o-ring seals or screw-top lids similar to glass jars. Plastics won’t shatter if dropped, and containers are re-usable if properly cleaned between specimens.

However, plastic can scratch over time, compromising clarity. Additionally, certain plastics may degrade with long-term preservative exposure or accumulate static charge that attracts contaminants.

Critical Features for Wet Specimen Jars

Beyond the basic material, other key features of jars for wet specimen storage include the lid and sealing method, opening size, and opacity.

Lids and Seals

An airtight, watertight seal is imperative to prevent evaporation and maintain specimen quality. Screw lids with rubber gaskets, glass lids with compression cam locks, and clamp-sealed rubber gaskets all provide excellent sealing against fluid loss.

Replaceable rubber gaskets allow refreshing the seal over decades of use. Silicone gaskets withstand chemicals better than standard rubber. Locking levers that compress the lid ensure a tight seal is maintained over time.

Jar Shape and Opening

Jar shape affects access to specimens. Wide mouth openings allow easier insertion and removal of specimens, while narrow necks limit evaporation from a smaller exposed surface.

Customized shapes, such as cylinder jars, can accommodate odd-shaped specimens. Select a jar opening that enables easy specimen placement while limiting fluid exposure to air when open.


Clear glass allows observation of specimens without disturbing them, while colored glass or plastic blocks light that can damage specimens. Some fluids like formaldehyde decompose under UV exposure.

Opaque jars prevent algae growth and provide privacy if classroom display is a goal. If monitoring specimen integrity is important, opt for clear or translucent materials.

Selecting the Best Jars for Your Needs

There are additional factors that come into play when selecting the optimal wet specimen jars based on your particular application and needs.

Storage Duration

Short-term wet specimen storage for just weeks or months has more flexibility in jar selection, while decades of preservation demand only archival-quality containers. In general, glass with silicone gaskets is recommended for long-term storage.

For collections intended to last generations, be prepared to periodically replace gaskets and inner seals to maintain airtight seals over an extensive timeframe.

Specimen Size and Shape

The container must be able to accommodate the full specimen with enough fluid to cover it. Irregularly shaped specimens may require odd-shaped jars or additional supports inside to hold the sample stable and avoid damage.

Leave ample headspace above the fluid to allow for periodic topping off as evaporation occurs. Custom jars can be ordered for especially large or uniquely shaped specimens.

Environmental Factors

Will the specimens be displayed in areas with temperature swings or UV light? Take measures to control light, humidity, and warmth to avoid algae growth and fluid evaporation. Certain plastics become brittle when cold.

Rotate specimens away from direct light. Add humidity controls to storage areas. Select jars made of material resistant to the preservative – glass tends to withstand chemicals and environmental fluctuations better than plastic.

When curating a wet specimen collection, investing in proper archival-grade jars helps preserve specimens for scientific study, education, and enjoyment for generations to come. Prioritize seal integrity, fluid-resistant materials, and customized sizing when selecting jars.

For most applications, we recommend glass containers with plastic inserts and polypropylene lids for an impermeable seal, or bail-top glass jars with neoprene gaskets for excellent compression seals. Wide mouth glass crocks with rubber gaskets also seal fluids reliably for large volume storage.

Monitor your collections periodically – change preservative fluids every few years, observe specimens through clear jars, and refresh gaskets as needed. With proper jars and attentive care, your wet specimens can remain intact indefinitely.

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