Kilner® Wax Discs for Jam Jars: Sizes, Sealing & How Many You Need

Quick answer

Kilner® Wax Discs come as a 200-pack with 100 discs at 5.5cm and 100 at 7.5cm, so most standard jam jars are covered without measuring. Use a disc only if you plan to store preserves without a full water bath; if you process jars in a boiling water bath, a two-piece lid is the safer seal.

Which wax disc size fits your jam jar?

The pack splits into two diameters: 5.5cm and 7.5cm. The smaller disc suits narrow-neck jars and small preserve jars, while the larger disc covers wider openings. A disc should sit flat on the surface of the jam with a small overlap at the glass edge, not fold up the sides. If your jar opening is between the two sizes, use the larger disc and trim it only if it buckles.

How to seal jam with wax discs

Fill the jar while the jam is still hot, leaving about 1cm of headspace. Drop a wax disc directly onto the surface so the heat softens it slightly and it molds to the jam. Press gently with a clean spoon to remove air pockets. Let the jar cool completely, then add a lid or cellophane cover. The wax disc is a surface barrier, not a substitute for a lid; it keeps the top of the jam from drying out and reduces exposure to air.

Do you need wax discs for jam?

No, not if you use a boiling water bath and a two-piece lid. Wax discs are a traditional extra step for open-pot preserves, low-sugar jams, or jars you plan to eat within a few months. If you are canning for shelf-stable storage, follow a tested water-bath process and skip the wax. If you are making a small batch for the fridge, a wax disc plus a lid is a practical way to keep the surface clean and fresh.

Wax disc vs lid for preserves

A lid creates a mechanical seal that can handle heat processing and longer storage. A wax disc creates a physical barrier on the jam surface but does not create a vacuum. For high-acid jams and jellies, a lid alone is usually enough. For lower-sugar or alcohol-spiked preserves, a wax disc under a lid adds a layer of protection against mold and drying. Use both when you want the traditional look and a cleaner top layer.

How many discs will you actually use?

One disc per jar. The 200-disc pack covers 200 jars, so it suits a heavy preserving season or several small batches. If you make jam once a year in a dozen jars, the pack will last multiple seasons when stored flat in a cool, dry place. Discs are not reusable once they have touched jam, so plan one per jar plus a spare for any jar you need to reseal after opening.

Storing and handling wax discs

Keep discs in their packaging or a sealed container away from heat and strong odors; wax can pick up smells from the cupboard. Handle with clean, dry hands or tweezers. If a disc cracks, it can still be used if it lies flat, but a torn disc leaves a gap. Discard any disc that has been sitting in direct sunlight or has visible grit.

Quick answers to common wax disc questions

Do I need wax discs if I use a water bath?

No. A tested water-bath process with a two-piece lid is sufficient for shelf-stable jam. Wax discs are optional and mainly used for open-pot or refrigerator preserves. Skip wax if you process; use wax if you store in the fridge.

Can I reuse a wax disc?

No. Once a disc has touched jam, it can carry moisture and contaminants. Use a fresh disc each time you seal a jar. One disc per jar, every time.

What if my jar opening is between 5.5cm and 7.5cm?

Choose the 7.5cm disc and press it flat. If it wrinkles at the edge, trim the excess with clean scissors before adding the lid. Size up, then trim if needed.

Product facts

• Kilner® Wax Discs for Sealing Jam Jars: Pack of 200 wax discs for sealing jam jars, with 100 discs at 5.5cm and 100 at 7.5cm. Two sizes in one pack mean you can seal small and wide jars without buying separate discs.
• Kilner® Wax Discs for Sealing Jam Jars: Ideal for use with Kilner® jars and other preserving containers. Works with your existing jar collection, not just one brand.
• Kilner® Sourdough Starter Set: The Kilner® Sourdough Starter Set contains all components needed to make a successful sourdough starter. If you also bake sourdough, this set covers the starter stage while your wax discs handle jam sealing.