Elastics and modern cloth nappies

Elastics are a component used in new modern cloth nappies. They are often the first part of the nappies that begins to show deterioration, either stretching out or becoming brittle and hard. We have compiled some information about what elastics are made from, what causes deterioration and how to replace elastics to help you get the most out of your nappies.

Elastics are included in modern cloth nappy shells, fitted nappies and even some inserts. How long they last can vary, eventually all elastics degrade and lose elasticity over time.

What is elastic made of

Elastic is made from either:

• natural rubber
  • made from the milky latex of various trees, usually the Hevea rubber tree
• synthetic elastomer from petroleum, 
• synthetic elastomer from silicone, or
• a combination of natural rubber and synthetic elastomer

The word elastomer describes a polymer with elasticity that has weak intermolecular binding. In the case of elastics, it is a material made from either natural rubber or synthetic elastic. 

Causes of elastic degradation

Cloth nappy inserts and covers are exposed to chemicals from urine, which turns into ammonia, poo, detergent, oxygen bleach, chlorine bleach, heat and agitation from the washing machine. Each of these factors contributes to the degradation of the elastic fibres. Depending on the type of elastomer used in the elastic, over time it will either harden or soften.

Exposure to heat, oxygen and/or light reduces the flexibility of the elastomer, and these are common conditions for reusable nappies.

Hardening is the most common form of failed elastics in cloth nappies. They become brittle and crunchy and when stretched out, lose their ability to retract. 

This hardening or softening can only be prevented or slowed down by the addition of UV stabilisers and antioxidants when the elastic is produced. It is impossible to predict whether they will become hard and brittle or stretched out and soft.

Whether the elastics soften or harden, the result will look the same; the elastic will stretch out and not return to its original length. 

Elastic failure occurs with age, and in some cases, prolonged storage before they have been worn or laundered. This means that elastics can fail even on the roll, having never even made it to a nappy.

Prolonging the lifespan of cloth nappy elastics

Ensure your nappies, underwear and other items with elastics are washed thoroughly, regularly and dried completely before being stored. Avoid letting soiled items sit for more than 24 hours before washing them. 

Storage conditions do not affect the lifespan of elastics substantially. The factors that result in degradation are how the elastic was made, its age, how much it was used, and how well it was washed and treated. Therefore, even under perfect storage conditions or even without being used, elastics will eventually fail and need to be replaced.

Storing nappies where they are not getting very hot or very cold, and storing nappies that are clean and very dry is the best way to prolong their lifespan. 

~ Clean Cloth Nappies admin team.

Replacing elastics in modern cloth nappies

Repairing elastics is achievable with hand sewing or a sewing machine. If you do not have the time (or inclination) to do this yourself, there are services (for example, your local repair cafe or tailor) that may be able to assist. There are also micro business that specialises in cloth nappy repairs.

Purchasing replacement elastic

Fabric supply stores sell a range of elastics. Most pattern groups recommend poly-braided elastic. 

The required elastic thickness varies between brands and styles; 8mm (5/16 inch) works well for day nappies and 12mm (approximately 1/2 inch) for night nappies. If you are unsure, take a nappy with you when you go to the fabric supply store. 

Sewing supplies

• Sewing machine or needle
• Seam ripper or embroidery scissors
• Replacement elastics
• Sewing thread
• Sewing pins
• Safety pin or yarn needle

Replacement method

Either hand stitch or machine sew. For best results with a sewing machine, use a straight stitch rather than zigzag stitch. 

These replacement instructions are for the most common style of modern cloth nappies. This style has elastic sewn and attached at one end, the elastic stretched through a hollow, narrow, enclosed channel, and then sewn and attached at the other end. 

1. Unstitch 3–4cm of the seam at both ends of the nappy where the elastic is attached.
   • Do not unstitch the entire seam, only each end where the elastics are attached. 
2. Remove the existing elastic.
3. Thread the new elastic through the channel from one end to the other.
   • Use a yarn needle or a safety pin as assistance.
   • It is often easier to trim the elastic to size after threading it through the channel.
4. Pin the elastic in place at each end.
5. Start at one end, stitch the new elastic to where the old one was previously attached. 
6. Stitch the over the first opening.
7. Stitch the other end of the elastic to the nappy. 
8. Stitch over the second opening. 
9. Repeat on the opposite leg.

Videos showing how to replace elastics in modern cloth nappies