A stone bathtub lifts a bathroom from ordinary to special, and it asks for a bit of extra care in return. Keep the surface clean, manage water spots, and protect it from harsh products, and you will keep that smooth, sculptural look for years. The trick is knowing what your tub is made from and what it can handle.
If you are in New Zealand, there are a few local factors to consider too. Our water hardness varies by region, many homes run hot water at 50 to 55°C, and bath bombs and essential oils are common in winter. All of that shows up on stone if the cleaning routine is off by even a little.
Why stone baths need special care
Natural stone is porous and reacts to acids and some alkalis. Marble, limestone and travertine can mark if lemony cleaners, vinegar or strong bathroom sprays touch the surface. Composite stone, often a blend of crushed stone and resin, is more stable but can still scratch or turn dull if you use abrasive powders.
Soap scum is the other big issue. It is a film of fatty acids that binds to minerals in water. In soft-water areas the film wipes off easily. In hard-water areas it locks together with calcium and magnesium, forming a stubborn haze. Leave that for a month and you will see a grey band at the water line.
New Zealand’s water makes a difference. Typical hardness figures:
● Auckland: 25 to 60 mg/L as CaCO3, generally soft
● Wellington region: 30 to 90 mg/L, soft to moderately hard
● Christchurch: 130 to 180 mg/L, hard groundwater
● Tauranga, Hamilton, Dunedin: usually 30 to 80 mg/L
Those numbers matter because the harder the water, the faster limescale forms, and the more careful you need to be with your weekly clean.
Know your stone
Stone baths, including the increasingly popular stone bathtub, fall into two broad groups. Natural stone baths are carved or assembled from marble, limestone, or similar. Composite stone baths use stone powder with a resin binder, often called solid surface or stone resin. Care overlaps, yet the tolerances differ.
Natural stone can etch if you use anything acidic. A single splash of vinegar at around pH 2 to 3 can leave a dull spot on marble. Composite stone resists acid better, but the resin can scuff if you use abrasive pads. Most bathroom multipurpose sprays sit between pH 9 and 11, which is too high for many stones and will slowly dull the finish.
After a quick look and a wipe, you can usually tell what you have.
● Natural marble or limestone: subtle veining, cool to the touch, slightly varied colour
● Composite stone solid surface: consistent colour, warm to the touch after a minute, matte or soft sheen
● Stone resin with gelcoat: slightly glossy top layer, very consistent look, often lighter weight than full stone
● Acrylic bath: lighter again, warm immediately, higher gloss, not a stone product
If you bought your bath from Domenic Bathroom, our team can confirm the exact material from your invoice or a quick photo. That is the fastest way to pick the right cleaner.
Daily and weekly routine that actually works
A simple wipe after each soak saves the weekend clean. Keep a soft microfibre cloth nearby. After draining, rinse the sides with the hand shower, then wipe dry. That 60 seconds stops most water marks.
Once a week, go a little deeper. Use a pH-neutral cleaner, often labelled pH 6 to 8, and a non-scratch cloth or sponge. Spray lightly, wait 2 to 3 minutes for the product to lift soap film, then rinse well and dry. If your water is hard, add a final towel dry to cut down the chalky ring that can show up as the bath dries.
Avoid vinegar, citrus sprays, bleach, oxygen bleach powders, and anything gritty. They feel effective on the day, then a month later the surface looks dull or patchy. If the label says bathroom descaler, tile cleaner or mould remover, that is usually a no for stone.
Keep a small kit under the vanity or in the linen cupboard for consistency.
● Microfibre cloths
● Soft sponge or non-scratch pad
● pH-neutral cleaner for stone-safe use
● Clean bucket and a squeegee
● Spare soft towel for drying
Monthly deep clean, without drama
Start with the gentlest step that works. Fill a bucket with warm water, add a small amount of pH-neutral cleaner, and damp wipe the whole surface. Rinse. If you see a faint band at the waterline, apply the cleaner neat to that strip, leave it for up to 5 minutes, then wipe and rinse.
A stone bathtub with a composite finish that has a matte solid-surface can handle a bit more attention if needed. Some manufacturers approve a non-scratch cream cleaner to restore the sheen. Always test a 2 cm patch on the back of the bath first. If the area dries evenly with no bloom or haze, you can continue.
For natural stone, stop short of creams and pastes unless the product is marked safe for marble or limestone. Stone-safe products will often advertise a neutral pH and list marble and travertine on the label. If you are unsure, ask us. We keep cleaners in store that match the baths we sell.
Stain and scratch fixes
Stains happen. Oils from bath products, dyes from bath bombs, and metal marks from jewellery can leave traces. The right response depends on the material and the type of mark. Here is a quick reference you can screenshot.
|
Mark type |
Likely cause |
Natural stone response |
Composite stone response |
Typical time |
|
Oily dark patch |
Body oils, bath oils |
Stone-safe poultice, baking soda + water paste, cover 24 hours |
pH-neutral degreaser, warm water soak |
1 to 2 days |
|
Grey metal streak |
Jewellery, razor, bucket |
Rub gently with microfibre and mild cleaner |
Non-scratch cream cleaner, light pressure |
10 minutes |
|
Pink or blue stain |
Bath bomb dye, shampoo |
Stone-safe oxygen-based stain remover, no acids |
Mild cleaner, repeat rinses |
1 hour |
|
Chalky white band |
Limescale + soap film |
Neutral cleaner, soft pad, repeat cycles |
Neutral cleaner or approved descaler for composite only, test first |
20 to 40 minutes |
|
Dull etched spot |
Acid contact, citrus, vinegar |
Professional refinishing or stone polish kit |
Light rub with approved polish, test spot |
Varies |
If a mark does not shift after two gentle cycles, do not reach for bleach. Take a photo in daylight and send it to our team. Many stains look worse when wet and fade after a safe treatment and dry time.
Light scratches on matte composite stone can sometimes be blended with a fine surface restorer. A quick hand rub, then a full rinse and dry, is often enough. Deep scratches or chips on natural stone need a stone professional. Those can usually be repaired on site.
Sealing natural stone so it stays calm
Sealing cuts down the risk of stains on marble and limestone. Many natural stone baths arrive pre-sealed. Even then, a top-up once or twice a year is smart. The water droplet test tells you when it is time. Place a few drops on a clean, dry area. If the stone darkens in under a minute, it is thirsty.
Choose a penetrating sealer rated for bathrooms. Water-based sealers are lower odour and easier for small spaces. Solvent-based sealers often last longer. Ventilate the room either way. Apply with a soft cloth or applicator pad in thin layers, leave it to soak for the time on the label, then wipe off any excess so it does not dry sticky. Two light coats beat one heavy coat.
Sealing does not make stone bulletproof. It buys time to wipe spills and reduces how quickly oils soak in. Cleaners still need to be neutral, and acids still need to stay out.
What to avoid, always
Short list, big impact. These are the habits that cause most trouble in stone baths.
● Strong acids: vinegar, citrus, brick or tile descalers, toilet cleaners
● Harsh alkalis: oven cleaner, strong bleach, grout haze removers
● Abrasives: scouring powders, steel wool, green kitchen pads
● Thermal shock: boiling water straight into an empty cold bath
● Trapped moisture: suction-cup bath mats left in place for days
● Heavy impacts: dropping bottles, tools, or fittings into the tub
Hard water and limescale across NZ
In Christchurch and parts of Canterbury, a faint white haze can show up even with a good weekly routine. That is normal with hard water. Do the wipe-down while the surface is still slightly damp, then towel dry. If the haze builds, repeat the weekly clean twice in one session, rather than reaching for a stronger product.
Avoid citric acid on natural stone. It strips limescale but etches marble. Some composite stone manufacturers allow mild acidic cleaners for limescale, but only if the label confirms it is safe. When in doubt, stick to neutral pH and patience. Two or three gentle passes usually beat one aggressive one.
If you use a bath pillow or mat, lift it after each soak. Underneath is where trapped moisture and minerals leave rings. A squeegee is handy for quick water removal too. Ten seconds of squeegeeing the walls can save ten minutes of scrubbing later.
Temperature, weight and installation realities
Hot water settings matter. NZ homes often have tempering valves set between 50 and 55°C at the tap to reduce scald risk. Stone does not like sudden extremes. If your bath is cold, start with warm water, then increase the temperature. Give it 30 seconds to adapt before going hotter. This reduces stress on the surface and the waste fitting.
Stone baths are heavy. Many sit around 150 to 250 kg empty. Filled, you are looking at 350 to 500 kg, depending on size and depth. If you are renovating a timber floor, allow for the load. A stable base and even support keep the bath square and reduce hairline cracks that can show up at the waste.
Avoid chemical drain openers. If the waste slows, use a plunger or a hair catch. Harsh drain chemicals can splash back and mark the surface or attack the finish around the overflow.
Product picks and support from Domenic Bathroom
We stock acrylic and composite stone baths in finishes that suit modern New Zealand homes, along with vanities, LED mirrors, basins, tapware and more. The goal is reliable products with clean lines that stand up to daily use. That includes making cleaning straightforward.
Ask in store for a pH-neutral cleaner that matches your bath, spare overflow covers, and microfibre packs. We can also source stone-safe sealers and explain how to apply them. If you are comparing bath materials, our team can walk you through the care needs and long-term look of each option.
You are welcome to visit our Auckland showroom at 15 Olive Road. Bring room photos or your floor plan. We help homeowners, designers and builders choose fittings that look good now and still feel right in five years.