News

Covering concrete surfaces and selection of surface coatings – cleaning the surface

Covering concrete surfaces and selection of surface coatings – cleaning the surface

Covering concrete surface is one of the most complex stages that also creates the most questions as the aim is rock-solid protection against all liquids and also maximum physical resistance to all kinds of usage.
At the same time, the surface of the concrete must not look like it has been covered and the original feel of the surface cannot be spoiled by the coating!!!

Basically, coatings are divided into two – those that are absorbed into the surface and superficial coatings.

Materials that are absorbed into the surface are oils and different waxes. Very different types of waxes and oils are used, for example, in the USA, the carnauba wax i.e. palm wax is widely used as the hardest natural wax (Carnauba wax). Soft waxes are also used, such as beeswax. The best natural oils are those that harden, i.e. polymerize, such as the good old linseed oil (here it has to be noted, that linseed oil has different fractions that behave differently when treated).

One type of oil-coating is also silicone oil, the high hydrophobia (Hydrophobia) of which creates suitable conditions for use as a worktop coating.

IMG_4551

Superficial coatings are those which are not absorbed in the surface of the concrete, such as different varnishes or resins. The most typical ones used are PU 4 (Polyurethane) varnishes. The world of polymers and polymer resins is wide and one option is also to use such polymer resins that are similar to the material used for making cast marble.

In addition to the aforementioned, there are different impregnating nano-coatings (fluids), which are fairly common in covering different natural stones and increasing their weather-proofness and staining capacity.

What to expect from a coating?

As has been said many times before, it is important that a coating would not hide the original surface of the concrete, but would provide sufficient protection against stains. The fear of what will happen to the worktop and whether it will become dirty quickly is usually groundless and many who have ordered a worktop have later said that their initial fears were largely unfounded.
Concrete floors provide an illustrative example – regardless of intensive use, they are completely OK after being cleaned.

Of course, nothing lasts forever and if you use a meat hammer directly on the worktop or cut on the worktop without cutting boards or tap the end of a knife against the worktop, damaging the surface and the surface coating is very probable. If you wish to use the worktop in such a way, concrete is probably not your best option.

…a customer came with a request that they wanted a very strong worktop (for them, concrete was associated with extreme strength) as they like to cook in the kitchen from dawn till dusk and  wanted a worktop that can withstand absolutely everything!!!….

… I recommended them a stainless-steel worktop, similar to those used at commercial kitchens, as this is the only material that endures both blows and cuts to a large extent. However, even those worktops are damaged in time, which means that use always has to be based on the principle of reasonability.

If our aim is ordinary use, which includes using cutting boards, trivets and ordinary kitchenware, there is no danger of permanently damaging the concrete surface. Here, it has to be kept in mind that even though the coating may be damaged, the liquid does not spread in the surface and usually the surface will return to its original state after drying and stains caused by oily liquids can be cleaned off.

What surface coating to choose – which do we offer?

Varnishing

  • PU varnishes are superficial coatings. We have developed a three-layer varnishing, in the course of which we cover the surface with a base varnish, which is in turn covered with a liquid-proof varnish and then a finishing varnish. Such a coating is waterproof and durable – it is probable that nothing will happen to it . However, such a coating cannot withstand cutting with a blade as this may damage the varnish and liquid will reach the worktop.
  • Positive sides of PU varnishes are that they do not significantly darken the colour of the worktop (wet surface effect) and finishing the surface with them leaves an impression of an uncoated, i.e. original surface.
  • PU varnishes do not require later follow-up processing.
  • The finishing of PU varnishes is opaque.
  • PU varnishes are not suitable for outdoor conditions!

IMG_0239

Waxing

Oils and waxes are absorbed in the surface. With oils and waxes, the processing (oiling/waxing) has to be repeated once a year. As the oil impregnates the surfaces, oiled surfaces can withstand intense use better, for example in public buildings. Oiled surfaces are darker and shine more than those covered with PU (semi-opaque). Oiled surfaces also look considerably more robust as oil impregnates the surface differently. The general appearance of the surface may take different shades in time as the oil is absorbed.

IMG_0333

  • Oils/waxes are suitable for outdoor conditions and intensely used rooms.
  • Oils/waxes make the surface significantly darker and may create an interesting pattern as they are absorbed.
  • Oils/waxes need time to “dry”, i.e. polymerize – a worktop processed with linseed oil will become “dry” only in 4-6 weeks (similar to the formerly used linseed oil paints, which took a long time to dry).
  • For best results, worktops need to be reprocessed once a year.

Other coatings for natural stones

Nano-coating – a coating developed by different producers to protect natural stone. We recommend it if the surface has to be impregnated, but the customer does not want an intensive change in the colour. It is suitable for outdoor conditions.

It is not very liquid-proof, becomes wet in about 1 hour, but the coating repels dirt, wherefore the surface will restore its original appearance after drying.

Mainly suitable for coating shelves, wall panels or other details, the use of which is not related to different liquids.

Cleaning a surface coating

Initial cleaning is similar to cleaning all common kitchen worktops – different cleaning agents may be used (it has to be kept in mind that strongly alkaline or acidic substances should not be in longer contact with the surface).
Very abrasive cleaning supplies should not be used with PU varnished worktops as there is a chance of physically damaging the varnish.
Most liquids that are absorbed into the surface will dry without a trace because base varnishes function as a membrane that filters larger dirt particles to the surface of the varnish. Simple cleaning and just letting the worktop dry will remove all traces.

Dyes (ink, red wine) will remain behind the layer of waterproof varnish, but should they pass this barrier (for example, in the area around the sink opening of the worktop), then acrylates have been added to the concrete mixture and these do not let liquids absorb deep into the material.
As liquids are not absorbed deep into the surface, also different stone cleaning supplies can be used. Thanks to low surface absorption, very dirty spots can later be polished over, but with worktops, this also requires them to be varnished or waxed again.

An example of how a sink that has been in use for a year and a half can look like new after being rinsed. The varnish on it works like a filter that does not allow dirt to set into the pores so that rinsing removes soap residue or other dirt from the surface without problems.

IMAG1822

The PU food-safe coating complies with the FDA standard 21 CFR 170-199 – The FDA has regulations for “food contact materials”– materials that are intended to be in contact with food. Food contact materials can be constructed from a variety of materials like plastics, rubber, paper, coatings, metal etc. During the contact of the food molecules can migrate from the food contact material to the food. Because of this, in many countries regulations are made to ensure food safety.  PU complies with all Food Contact Materials listed with the FDA.