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How to use Rob Parker’s Best ConClear to remove cement stains

Rob Parker’s Best ConClear is an effective cement stain remover product in our comprehensive range of stone care products. It is effective at removing cement stains from stone whilst being much more gentle on the environment than other available alternatives.

Used correctly you will achieve great results every time. We have put together some further hints and tips that will help you achieve great success with our product.

Please read through this article before using Conclear, as extra care should be taken on limestone, and Kandla Grey sandstone.

Remove cement stains from stone surfaces with Rob Parkers Best Conclear

How does cement staining occur?

Cement staining often occurs after spillage of mortar during the pointing of a patio. This could be due to excess mortar spilling out of the pointing joints. Cement staining can also occur as a result of fingerprints or footprints during the slab laying stage. Another reason for cement staining can be spillage of mortar from the pointing or rendering of a wall that overhangs a paved area. The cement stains may be recent, or you may have existing stains on paving that you wish to remove.

How different mortar mixes will react with stone

The mortar mix used in any of the above jobs could be different both in the ratio of cement to sand, the type of sand used, and the amount of moisture in the mortar mix. The cement stain may also have been on the stone for varying lengths of time e.g., a few hours, days, or much longer.

Rob Parker’s Best Conclear can tackle all these issues, but you will now understand that in some cases a different method of usage may be required to achieve a good result.

Mortar mixes differ, and in turn their chemical make-up will react differently with all products, including ConClear.

For example, at Stoneworld we advise that the ideal mortar to use for laying a sandstone patio is a 5 : 1 ratio of mixed sand (mixed sand : 50% sharp/50% soft sand) to cement. If 100% sharp sand is used a stronger mortar occurs. If the mortar is mixed for brickwork, or pointing the patio, the ratio is likely to be 3 : 1 making an even harder mortar.

Harder, stronger and older mortar stains will require more effort to remove.

NB. ConClear will NOT remove staining caused by resin based jointing compounds such as Resiply. Buy an appropriate product that will dissolve polymers in resin such as Rob Parker’s Best Stone Stripper.

Stoneworld do not recommend the dry mortar mix method of pointing a patio


We know that some landscapers use a dry mix of cement & sand for pointing, which is brushed in dry and then hosed to moisten, creating a mortar in situ.

Firstly, we would not advise this method of pointing anyway, as we recommend ResiDUAL which will give superior results. Find out about ResiDUAL here.

However, we want to illustrate a further cement staining problem that can occur using this dry mortar mix method of pointing.

If the sand in the dry pointing mix is overly dry, the cement powder tends to separate when the brushed in mix is hosed. This spills out over the slabs in the hosed water. The result is a fine cement film over the patio surface with cement particles set hard in the surface pores of the stone. Where the cement has separated, a 1 : 1 ratio mortar has been inadvertently created – this is a super strong mortar and very difficult to remove.

ConClear will tackle all these cement stains, but you will need to take heed of these further tips supplied here. Furthermore, as all stone and mortar mixes are different, we advise you to try a test patch first, so that you can watch how quickly it reacts in your particular situation.

Keep a clean workplace to reduce cement staining

To avoid cement staining occurring, Stoneworld recommend keeping your work area as clean as possible clean during the project. Remember, cement dust left on the surface can become 1 : 1 mortar if accidentally moistened. As a result, we recommend to wash off footprints and finger marks at the end of each day during the project.

After laying the paving, have a thorough clean-up before starting the pointing phase of the project. This will prevent any cement stains having time to dry out and stick more firmly to the surface than was necessary- why make more hard work for yourself?

Failure to do the above could result in cement stains of various strengths hardening on the patio surface, making it more difficult to clean up easily at the end of the project.

How to Use ConClear

We advise you to try a test patch first, so that you can watch how quickly it reacts in your particular situation.

  • Use neat or diluted with water (up to 1 vol. of CONCLEAR with 2 vols. of water)
  • IMPORTANT: Shake the closed container for 30 seconds before opening for use.
  • Pre-wet the area to be cleaned with water.
  • Apply evenly over the contaminated area, using a low-pressure sprayer.
  • A heavy initial application should be made when cleaning off cement and concrete residuals that are old and thick.
  • Re-apply after 10 minutes.
  • Leave for a minimum contact time of 45mins.* Take care on limestone. We suggest a test & measure approach ** for black limestone & Kandla Grey Sandstone see below
  • It is important to keep the treated surface moist during the treatment stage as a dry surface means the cleaning reaction has stopped. (Cover to protect from evaporation if necessary).
  • Rinse off thoroughly with water using a pressure washer.

NB. On all limestone surfaces, but especially dark limestones, we advise you to use with caution

NB. On Black Limestone– Use on affected area only, dabbing & removing frequently until desired effect is achieved. Do not leave on surface for longer than necessary to remove cement residue. Do not allow to dry.

NB. On Kandla Grey sandstone– Use for the minimum time required to remove the cement spills, i.e. be diligent and watch for the cement to dissolve, then rinse immediately. Otherwise you risk activating the natural iron deposits within the stone. These can be successfully removed with another of our products: Rob Parker’s Rust Remover, BUT save yourself the extra work and expense by being mindful of this advice.

The instructions we print on the bottle cover a broad spectrum of situations, but here we can go into more detail on specific issues.

How Conclear works

Conclear works by dissolving the cement residue. To do this it needs moisture in the cement stain.

Dampen – do not saturate!

If you use too much water to pre-wet the area, then the ConClear will become diluted. Plus, an over wet surface may enable ConClear to travel away from the stain.

Do not use ConClear on a dry cement stain. Moisture will be drawn from the product. This will inhibit activation and it will not work.

Therefore, we advise using ConClear on dampened cement stains. Activation is normally swift and effective.

However, for stubborn stains on sandstone, it is advisable to cover the treated area with plastic to prevent evaporation. This will elongate the activation period.

Evaporation will deactivate the treatment.

Conclear is far gentler than brick acid. Brick acid burns into the surface of stone, and can permanently damage materials.

It is an inert substance that will not activate on any substrate other than cement formulations.

ConClear does not work on resin-based pointing mixtures (e.g. ResiDUAL) To remove resin-based pointing we recommend Rob Parkers Best Stone Stripper

Take extra care when using Conclear on Black Limestone and other limestone surfaces.

When using Conclear on limestone paving we do not recommend leaving for prolonged periods. Use just long enough to remove the cement. If you accidentally leave too long, a cloudy film may form, which will alter the appearance of Black Limestone. Do not despair! This is a residue from ConClear. Remove using hot water with a scrubbing brush and sharp sand. Alternatively, use a domestic green scourer.

At Stoneworld we are always available to help our customers. You can call us on 01844 279274 or email us at sales@stoneworld.co.uk for advice on your specific issue if you don’t find the answer here.