Painting over silicone sealant is one of the most common causes of premature paint failure in Melbourne homes. The problem isn't the paint. It isn't the surface preparation. It's the sealant itself, because standard silicone forms a non-porous, flexible film that no water-based or oil-based paint can bond to reliably. If you've seen peeling strips around bathroom trims, window reveals or skirting boards, silicone is almost certainly underneath.
Why silicone and paint don't mix
Silicone cures into a rubber-like compound that repels moisture by design. That's exactly why tradies reach for it around wet areas. But the same chemistry that stops water from penetrating also stops paint from adhering. Brush or roll over it and the paint film sits on top rather than bonding to the substrate. Within weeks, sometimes days, it begins to peel off in strips or bubbles up at the edges.
Acrylic sealant is a different story. Paintable acrylic sealant cures to a harder, less flexible finish and accepts a top coat without drama. The trouble is that silicone and acrylic sealants look nearly identical once applied, so many homeowners don't know which one they're dealing with until the paint starts lifting.
The quick test: drag a fingernail across the cured sealant. If it stretches slightly without breaking, it's silicone. If it feels more rigid and chalky, it's likely paintable acrylic. You can also do a water test: silicone beads water, acrylic absorbs it slowly.
Your two options when silicone is already there
There are really only two paths forward. Remove the silicone entirely, or encapsulate it. Both work, but they suit different situations.
Option 1: Remove and replace. This is the right approach for most interior jobs, particularly around bathrooms, laundries, windows and skirtings. Use a dedicated silicone remover product (Selleys Silicone Remover is widely available at Bunnings across Melbourne) and a plastic scraper to avoid marking the substrate. Work in sections, apply the remover, let it soften the sealant for 30 to 60 minutes, then scrape and wipe clean. Once all traces are gone, replace with a paintable acrylic sealant, let it cure fully (check the product data sheet, usually 24 hours minimum), then paint over it.
Option 2: Encapsulate with shellac or oil-based primer. If removal is impractical, a shellac-based primer (Zinsser BIN is the most reliable) can bond to silicone better than any standard primer. Apply two coats with a fine brush directly over the sealant. Let each coat dry fully. Then apply your topcoat. This won't hold forever on a high-flex joint that moves with temperature changes, but on stable, low-movement joints it can last several years.
Dealing with silicone around wet areas
Bathrooms and laundries are where this problem turns up most often. The junction between the bath or shower base and the wall tile, or between the vanity and the wall, is almost always sealed with silicone for good reason: the joint flexes with foot traffic and thermal movement. You don't actually want paint there. You want fresh, clean sealant that matches or complements the wall colour.
The best outcome in a bathroom isn't painting over the sealant. It's removing old silicone, cleaning the joint thoroughly, applying fresh silicone in a colour that suits the room, and painting up to (but not over) the joint. If you're choosing colours for a bathroom from scratch, using paint to make a small bathroom feel larger is worth reading alongside this process, because the colour you land on will determine how visible the sealant line is.
Mould is a related issue. Old silicone often turns black at the surface long before it fails structurally. If the sealant is mouldy, no primer or paint will hide it for long. Cut it out, clean the substrate with sugar soap and a diluted bleach solution, let it dry completely, then apply fresh sealant.
The prep sequence that actually works
Whether you remove and replace or encapsulate, the sequence matters. Cut corners here and the sealant line will be the first thing to fail after a repaint.
- Remove or mechanically key the existing silicone (fine 120-grit wet-and-dry paper can abrade the surface slightly if full removal isn't an option)
- Degrease with mineral spirits or a silicone remover residue wash
- Apply shellac primer to the sealant zone specifically, not just a skim of water-based undercoat
- Let each primer coat dry before touching up or topcoating
- Apply the topcoat without overloading the brush at the sealant edge
One thing worth doing before you start: check whether the room has a broader moisture problem. Condensation, poor ventilation and leaks all attack paint at the same spots where sealant fails. If you're also dealing with those issues, treating them before repainting will protect the new finish far longer.
What to use at skirting boards and architraves
Skirting boards and architraves are commonly sealed with silicone at the floor or wall junction, particularly in newer builds. This is arguably the wrong product for the job (paintable acrylic or decorator's caulk would have been the better choice), but it's what you'll find. When you're repainting trims, run the same removal and shellac primer process over any silicone-sealed joints before applying your semi-gloss or gloss topcoat. If you're tackling skirting boards and architraves as a broader project, painting skirting boards and architraves to a professional standard covers the full technique in detail.
One shortcut that doesn't work: caulking over existing silicone with acrylic caulk. The acrylic won't bond to the silicone any more reliably than the paint will. You'll get the same peeling, just with an extra layer of product involved.
Product choices that matter
For removal: Selleys Silicone Remover is the most accessible option for Melbourne homeowners. For shellac primer: Zinsser BIN in the spray can version is useful for tight joints; the brush-on version works better over larger sealant runs. For replacement sealant: use a product specifically labelled "paintable" or "decorator's caulk" rather than a standard silicone, unless the joint genuinely needs silicone's flexibility.
The label matters. Many sealants on the shelf are marketed for kitchens or bathrooms, which implies silicone content. Read the fine print and look for "overpaintable" on the front panel before buying.
When to call a painter
If the silicone runs around an entire kitchen splashback, multiple window reveals or an extensively tiled bathroom, removal is time-consuming and getting a clean finish at the replacement joint is a skill. A professional painter working on a full interior repaint will deal with sealant joints as part of the prep process. Apex Painting handles the full prep sequence on Melbourne residential jobs, including sealant removal, priming and joint replacement, so the topcoat isn't compromised before a brush ever touches the wall colour.