The Stain Library

Material

Silicone sealant

A soft bead attached to two surfaces, damaged by vinegar, bicarbonate and bleach according to its makers, and replaced rather than cleaned once mould is in it.

  • SurfaceSemi porous
  • WashingSpot only
  • Colour run riskLow
  • Reviewed7 September 2026

What silicone sealant can and cannot take

  • Heat Use with care
  • Water and soaking Tolerates it
  • Acids, including vinegar Avoid
  • Strong alkalis Use with care
  • Solvents Avoid
  • Chlorine bleach Avoid
  • Abrasives Avoid

General rules for silicone sealant

The bead is soft, slightly porous at the surface, and permanently attached to two other surfaces, which is what makes it awkward.

For a fresh milk mark, warm soapy water and a soft brush along the joint is enough, and it matters because organic residue left in a joint is what mould grows on afterwards.

Do not reach for vinegar, bicarbonate or bleach as a first move. The maker excludes all three, and a damaged bead is a resealing job.

Check the label

Sealant manufacturers say that vinegar, bicarbonate of soda and bleach do not kill mould spores and have the potential to damage the sealant bead, and that a specialist bathroom mould and mildew remover is the correct product. Where mould has penetrated the bead, it has to be cut out and replaced.

Stains on silicone sealant

Silicone sealant is a cured elastomer bead sealing the joint between two surfaces.

It is the collecting point

Everything on a worktop, a bath or a shower tray runs to the edge, and the edge is the sealant. That is why joints get dirty and why a smell in a bathroom so often comes from a bead rather than a surface.

The manufacturer excludes the usual remedies

UniBond states that vinegar, bicarbonate of soda and bleach do not kill mould spores and can damage the sealant bead, and recommends a specialist mould and mildew remover instead. That contradicts most household advice and it comes from the people who make the product.

Mould grows into it

Once it has, no cleaner reaches it, and cutting the bead out and resealing is the answer.

It is cheap to replace

A cartridge of sealant costs a few pounds and resealing a bath is an afternoon.

Sources

What we checked and when. Where a manufacturer instruction disagrees with anything here, follow the manufacturer.

  1. How to clean silicone sealant, UniBond manufacturer

    Sealant manufacturer guidance that a specialist bathroom mould and mildew remover is the correct product for silicone sealant, that vinegar, bicarbonate of soda and bleach do not kill mould spores and have the potential to damage the sealant bead, and that where mould has penetrated too deeply into the sealant the bead has to be cut out and replaced rather than cleaned.

    Checked 7 September 2026

  2. Bathroom care guide, Carryduff Designs manufacturer

    UK bathroom supplier guidance that acrylic is softer than china and scratches, that scouring products are not recommended, that chemicals including nail varnish remover, household bleach, perfume and strong disinfectant must never be used on acrylic, that warm soapy water or a mild cream cleaner is the correct clean, that mild limescale removers are acceptable occasionally, that bleach must not go in a cistern, and that cleaners must never be mixed because they give off poisonous gas.

    Checked 7 September 2026

  3. Cleaning grout, Tile Council of North America trade body

    Tile trade body guidance that grout manufacturers do not advocate the use of acids because acids attack the cement in the grout, that grout is alkaline based and is dissolved by acids, that mildly alkaline cleaners are preferred over acidic ones, that oil and wax based cleaners leave a film that attracts dirt, that alkaline cleaner not properly rinsed leaves a sticky residue, and that cementitious grout should be sealed to prevent staining.

    Checked 7 September 2026