Stains on microcement: how to remove each type and stop them coming back

A stain on microcement is almost never a stain on the microcement: it is a stain on the varnish that protects it. That changes the way you have to treat it completely. As long as the varnish is intact, wine, oil or limescale stay on the surface and come off with warm water, pH-neutral soap and a cloth; the problem appears when an aggressive product is used that damages the varnish, or when the stain has been sitting for hours on an area that is already worn. In this guide you will see what the varnish resists and for how long, according to its datasheet, which products you should never use, how to remove each type of stain and what to do when the mark no longer comes out.

Everything that follows refers to ready-to-use microcement sealed with Smart Varnish, which is the varnish that comes with every Smartcret kit. If yours is from another manufacturer, the general principle is the same, but the times and the resistances may vary.

What the microcement varnish resists and how long you have

The Smart Varnish datasheet includes a chemical resistance table: on three coats of varnish cured for seven days, each substance is left in contact for 1, 3 and 8 hours and the result is scored from 5 (no visible change) to 1 (a mark that affects the surface). These are the values, with the varnish on its own and with the varnish mixed with Smart Booster, the component B added in bathrooms, kitchens, floors, outdoors and on furniture:

Three rules come out of this table. The first: almost nothing that gets spilled in a home leaves a mark if you clean it within the first hour; among the household substances (water, soap, oil, vinegar and wine) wine is the only one that already scores 4 at one hour on varnish without Booster, and with Booster not even that. What does mark from the first hour are ammonia, surgical spirit and hydrochloric acid cleaner, that is, cleaning products that should not touch the varnish. The second: time is what turns a splash into a stain; bleach goes from 5 to 2 between the first hour and the eighth. The third: the products the varnish handles worst are precisely the ones recommended in many home remedies: surgical spirit, hydrochloric acid cleaner, ammonia and bleach. That is why the next section comes before the methods.

What you should not use on microcement

The varnish is a water-based polyurethane film a few tenths of a millimetre thick. What attacks it is not the dirt, but the product used to try to remove it. These are the ones that are ruled out, and why:

• Vinegar and lemon juice. They are acids. On varnish without Booster vinegar drops to 4 from three hours onwards, and lemon, which is more acidic, can leave marks. If you were looking for “cleaning microcement with vinegar” for limescale, the answer is in the limescale section: it is not necessary and it is not advisable.
• Hydrochloric acid cleaner and limescale removers. Diluted hydrochloric acid: it is the worst score in the table (3 at one hour, 2 at three hours). It marks the varnish permanently.
• Bleach and ammonia. They withstand a quick clean, but not prolonged contact; and if the varnish is worn, they reach the microcement and discolour it.
• Surgical spirit and solvents. The 70 % alcohol scores 2 from the first hour. It takes away the sheen and, over time, the film.
• Green scourers, wire brushes, sandpaper and powder cleaners. They do not stain: they scratch. The matt scratching shows more than the stain you wanted to remove.

What does work: warm water, pH-neutral soap, microfibre cloths, non-abrasive sponges and kitchen paper to absorb. And for any stain that does not come out with soap, the cleaner we recommend is Smart Cleaner: it is formulated for sealed microcement, it is mildly alkaline (pH 9-10), biodegradable and highly concentrated (40-50 ml per 5-litre bucket), so a 5 L container at $63 (shown in your currency at checkout) gives between 100 and 125 washes. It is the same one used in every instruction in this guide.

The basic method, valid for almost every stain

Before looking for a remedy by type of stain, always apply this sequence. It resolves most cases and damages nothing:

1. Absorb, do not spread. With kitchen paper or a dry cloth, press down on the liquid without dragging it. If it is something solid or greasy, lift it off with a plastic spatula or the edge of a card.
2. Warm water and pH-neutral soap. A few drops in a litre of warm water; soft sponge, circular movements without pressing.
3. If a mark remains, Smart Cleaner. Dilute 40-50 ml in 5 litres of water (the dose on the datasheet), go over it with the sponge or the mop and leave it to work for two or three minutes on the stain. For an isolated stain, you can make up the same proportion in a smaller amount: 8-10 ml in one litre.
4. Rinse and dry. Rinsing is essential: the varnish datasheet warns that soap or detergent residues that dry on it can leave marks or streaks. Dry with a clean cloth so that no water rings are left.

There is one precaution about timing: if the varnish is recent, wait at least two weeks from its application before using Smart Cleaner or Smart Wax. Until then, only water and a cloth.

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How to remove each type of stain

Grease and oil

This is the most frequent stain in kitchens and on countertops and, according to the table, the least worrying: oil scores 5 even at eight hours. What looks like a grease stain is usually a film that cleans off with nothing more. Absorb the excess with paper, go over it with warm water and pH-neutral soap and rinse. If the varnish is matt in that area and the mark persists, it is because the grease has settled into micro-scratches in the worn varnish: Smart Cleaner, which is alkaline and dissolves grease, and then a coat of wax to even out the appearance.

Wine, coffee, tea and coloured soft drinks

These are the pigment stains. Wine is the substance that marks varnish without Booster soonest (4 at the first hour, 3 from three hours onwards), so here time really does count: absorb as soon as possible, without rubbing, and clean with warm water and soap. If a shadow is left once it dries, diluted Smart Cleaner with two or three minutes to work; repeat a second time rather than rubbing harder. On varnish with Booster (the bathrooms, kitchens and floors of the kits) wine holds at 5 up to three hours, so a glass spilled at a dinner and cleaned up at the end of it leaves no trace.

Limescale in the bathroom and the shower

Limescale is not a stain: it is a mineral deposit left behind when the water evaporates. It builds up around the taps, on the shower screen and on the lower part of the shower walls. The reflex of attacking it with vinegar or a limescale remover is the most common mistake, because both are acids and the varnish does feel them; the deposit, on the other hand, is recent and soft, and comes off with Smart Cleaner and a sponge, leaving the product to work for a few minutes and rinsing thoroughly. When the crust is old, go over it two or three times on different days rather than stepping up the aggressiveness of the product.

Prevention is the easy part: run a squeegee or a cloth over the screen and the walls after every shower. Without standing water there is no evaporation and no limescale, and you avoid mould at the same time. If you are thinking about the bathroom, the guide to the microcement shower explains how it is done and what falls the shower tray needs.

Rust

It appears where a metal object has been left damp on the surface: the leg of an outdoor chair, a spray can in the bathroom, a tool on the terrace. The rust is not produced by the microcement, it is deposited by the object. First remove the object and clean with Smart Cleaner; the superficial orange mark usually comes off. Do not use lemon or any acid rust remover: they take the rust away and the varnish with it. If the stain has penetrated because the varnish in that area was worn, the solution is the one in the last section, sanding and varnishing again, and while you are at it put rubber or felt pads under anything metallic.

Mould and black damp marks

Mould grows where there is standing moisture and little ventilation: corners of the shower, the joints between wall and tray, behind the screen. On the varnish it stays on the surface; it is cleaned with Smart Cleaner, a soft-bristle brush and a rinse, and then dried thoroughly. Avoid using bleach as a matter of course: at eight hours it scores 2 on varnish without Booster, and in a corner it tends to stay there longer than you think. If the mould comes back, the problem is not the cleaning but the ventilation or an area where the water does not drain away; correct that first, because no wax is going to make up for it.

Soap, detergent and water rings

These are the most common marks in showers and kitchens and the least often identified: whitish or shiny marks in the shape of a drop or a puddle. They are produced by the cleaning product itself when it dries on the varnish without being rinsed off; the datasheet warns about this expressly. They come off with warm water and a microfibre cloth, and they disappear for good as soon as you take up the habit of rinsing and drying after washing.

Scuffs and grey marks from rubber or metal

Dark soles, the castors of a chair or the legs of a piece of furniture leave grey marks that are not dirt but transferred material. They come off with a slightly damp cloth and pH-neutral soap without hard rubbing. If the mark is a real scratch and not a transfer, Smart Wax disguises the superficial ones; the deep ones need varnish.

When the stain does not come out: sanding and renewing the varnish

If after two attempts with Smart Cleaner the mark is still there, it has gone through the varnish and is in the microcement, or the varnish in that area is worn and absorbs. No amount of cleaning is going to solve it; the varnish will. The procedure is the same as in the initial application, on the affected area or on the whole surface if the wear is general:

1. Clean with Smart Cleaner, rinse and leave to dry completely.
2. Sand gently with grit 400 to open up the old varnish and take off the surface mark; remove the dust with a damp cloth.
3. Apply three coats of Smart Varnish with a roller, leaving 4 hours between coats and sanding the first and the second with grit 400. In bathrooms, kitchens and floors, mix the varnish with Smart Booster (50 g per litre), which is what gives the high scores in the table.
4. Wait 7 days for full curing before normal use, and two weeks before using Smart Cleaner or wax again.

One litre of Smart Varnish ($44) covers about 5 m² (about 54 sq ft) with the three coats, so to renew the varnish of a 6 m² bathroom the 2 L container ($72) is enough. If the damaged area is extensive or the microcement is chipped, it can be recoated on top with the microcement kit for floors and stairs or the microcement kit for the bathroom, without removing anything.

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How to stop them coming back: varnish, wax and routine

Prevention has three layers and it is worth being clear about them, because they are not interchangeable.

The varnish is the protection. It is what appears in the resistance table; without it, microcement absorbs like a mortar. In bathrooms, kitchens, floors, outdoors and on furniture it has to carry Smart Booster, and the kits for those areas already include it. Check its condition every six months (matt areas, rings that were not left before, water that no longer beads) and renew it at most every 2 years in bathrooms, kitchens and surfaces with damp or traffic, and every 3-4 years in bedrooms, living rooms and offices.

The wax is the maintenance. Smart Wax is applied over the varnish, diluted (20-25 ml per 7 litres of water for application by hand), with a mop or microfibre, in a thin coat and without rinsing; it dries in 12-24 hours. It adds shine, improves surface hardness and makes water and splashes run off, but it does not replace the varnish and it does not cover up a worn varnish. It is renewed every 6-12 months depending on use: sooner on floors with traffic and in damp areas, later on walls. The full method is in the guide to wax for microcement.

The routine is what prevents 90 % of stains. Cleaning up spills at the time, washing with water and pH-neutral soap or Smart Cleaner one to three times a week depending on use, rinsing and drying, and not leaving damp metal objects or pots without a saucer on the surface. It is set out in full, with the most common mistakes, in how to care for and clean microcement at home.

Our recommendation for having the three layers covered is simple: Smart Cleaner for the weekly cleaning and for stains (5 L, $63), Smart Wax for maintenance waxing every 6-12 months (5 L, $61) and Smart Varnish with Smart Booster for renewing the varnish when the time comes (1 L $44, 2 L $72, 5 L $153, in matt or satin; 50 g Booster at $12, the dose for one litre). All three are in the cleaning and maintenance collection, and they are the same products the kits are applied with, so there are no incompatibilities between what you have on the floor and what you use to look after it.

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Summary by type of stain

Frequently asked questions about stains on microcement

Can microcement be cleaned with vinegar?

It is not advisable. Vinegar is acidic and, although the varnish resists it for an hour with no change, from three hours onwards it already leaves a mark on varnish without Booster, and diluted half and half with water it is still acidic. For limescale, which is the usual reason for using it, Smart Cleaner or pH-neutral soap and drying the shower after each use are enough.

How long can a stain sit before it becomes permanent?

It depends on the substance and on the varnish. According to the datasheet, with varnish without Booster wine marks slightly at one hour and visibly at three; oil and water do not mark even at eight. With Smart Booster, wine, vinegar, oil, soap, water, bleach and ammonia leave no visible change up to three hours, and at eight hours wine, bleach and ammonia mark only slightly; surgical spirit and hydrochloric acid cleaner are the only ones that leave a visible mark even with Booster. The practical rule: clean within the first hour and you will not have to consult the table.

Is bicarbonate of soda any use on microcement?

As a dry absorbent on a recent grease stain, yes, and it does not damage the varnish. As a paste to rub with, no: it is a mild abrasive and it can dull the varnish. Anything bicarbonate of soda might do, Smart Cleaner does without scratching.

The stain has come out but the area looks more matt than the rest, what do I do?

That is wear of the varnish from the cleaning, not a stain. A coat of Smart Wax evens out the sheen in most cases. If the difference is still noticeable, renew the varnish in that area with three coats of Smart Varnish.

How do I keep a microcement shower free of stains?

A squeegee or a cloth on the screen and the walls after every shower, a weekly wash with Smart Cleaner and a rinse, wax every 6-12 months depending on use and a varnish check at most every two years. And a check on the fall of the shower tray: water that does not reach the drain is the origin of limescale and of mould.

If you have a stain right now and you do not know what it is, start with the basic method using Smart Cleaner and message us on WhatsApp with a photo: we will tell you whether it will come out with cleaning or whether it is time to renew the varnish.

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