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Sealed Microdur Plus microcement in the lounge at Maysan, LXR Doha
Specification and technical data

Primers and sealers — specification and technical data

The primer and the sealer are part of the system, not an accessory to it. Most finish failures we are called to inspect trace back to the wrong primer, or a sealer applied before the substrate was dry enough. Both carry their own data sheets and both belong in the specification.

The system

What sits against what, from the substrate outwards. Junctions, movement joints and edge details are project-specific — send us the drawings and we will mark them up.

Priming and sealing sequence

The moisture reading, not the calendar, decides when the sealer goes on.

BUILD ORDER — SUBSTRATE FIRST, IN SEQUENCE Substrate check
Clean, consolidated, free of grease. Moisture measured with an instrument designed for the purpose.
 Primer
Primer 100 on absorbent and non-absorbent mineral substrates; AURO No. 301 on strongly or irregularly absorbent plaster and plasterboard under clay finishes.
 Wait
Primer 100: minimum 30 minutes and not more than 8 hours before the first finish coat.
 Finish
Applied to the finish system's own specification.
 Sealer
24 to 48 hours after the finish has hardened, at below 5% moisture. Maxipur recoat at 4 hours, maximum 3 days.

Performance data

Taken from the manufacturers' own technical data sheets, with the standard each figure was measured against. Product-level figures are on the product pages below.

Property Result Standard
Primer 100 — consumption 6 – 8 m²/L per coat, undiluted Cemher data sheet
Primer 100 — touch dry 30 minutes; overcoat window 30 minutes to 8 hours Cemher data sheet
Primer 100 — VOC Declared VOC content nil in the manufacturer's data sheet — ask us for the content certificate before specifying against a VOC limit Cemher data sheet
Primer 100 — application range 0 °C to 30 °C; density 1.04 g/cm³ Cemher data sheet
Maxipur 100% — consumption 8 – 9 m²/L Cemher data sheet
Maxipur 100% — drying Touch dry 4 hours at 23 °C; fully dry 24 hours; recoat 4 hours to 3 days Cemher data sheet
Maxipur 100% — type Two-component aliphatic acrylic polyurethane, gloss, satin or matt Cemher data sheet
Maxipur 100% — conditions 12 – 25 °C, relative humidity below 80% Cemher data sheet
AURO No. 301 — consumption Approx. 0.05 L/m² per coat; dilute 1:1 with water for priming AURO data sheet
AURO No. 301 — drying Re-coatable after 4 to 6 hours; fully dry after 48 hours AURO data sheet
AURO No. 301 — VOC Product VOC < 1 g/L against an EU limit of 30 g/L (2004/42/EC II A (a)(Wb)) AURO data sheet
AURO No. 301 — permeability Open-pored, DC value < 0.1 m AURO data sheet

Products in this family

One page per technical data sheet. Each carries the manufacturer's declared figures, the limits, a specification clause and the full document set.

Cemher Primer 100 Water-based adhesion promoter The adhesion promoter that goes under the Cemher systems. Used undiluted, it takes both absorbent and non-absorbent substrates, and it has a defined overcoat window — a minimum of 30 minutes and a maximum of 8 hours. Cemher Maxipur 100% Two-component polyurethane sealer — gloss, satin, matt The solvent-based sealer for the Cemher systems: a two-component aliphatic acrylic polyurethane with high chemical resistance, in gloss, satin or matt. The recoat window is 4 hours to 3 days — miss it and the surface has to be abraded. AURO Pflanzenchemie AG AURO Plaster Primer No. 301 Plaster primer A solvent-free, low-emission water-based primer for strongly or irregularly absorbent mineral surfaces under clay finishes. It evens out suction so the clay coat pulls uniformly, and it stays open-pored so the wall keeps breathing.

Where not to use it

Specifying a material into the wrong place is the most expensive mistake on a finishes package. These are the limits we will raise at review whether or not they are asked about.

  • Maxipur is solvent-based. Specify Aquamax where a water-based sealer is required.
  • Sealing before the finish is below 5% moisture traps water in the build-up.
  • Primer 100 must be used undiluted.
  • AURO No. 301 is for mineral interior substrates under clay finishes, not a general-purpose primer.
  • Shelf life 24 months for all three, stored cool, dry and frost-free.
Specification clause

Primers and sealers: Cemher Primer 100 adhesion promoter applied undiluted at 6–8 m²/L, first finish coat applied not less than 30 minutes and not more than 8 hours afterwards. Finish sealed with Cemher [Maxipur 100% two-component polyurethane in matt / satin / gloss] at 8–9 m²/L, applied not less than 24 hours after the finish has hardened and only when substrate moisture is below 5% measured by meter. Recoat interval 4 hours, maximum 3 days.

Square brackets mark the choices that belong to the project. Send us the finishes schedule and we will return the clause completed, with the sample and mock-up programme against it.

Document library

Every publishable document for this family, reproduced in full and unaltered under our cover. Free to download, no form.

Featured projects

Built with this material, by our own artisans. Open the project for the full set of photographs and the story of the installation.

Sealed Microdur Plus microcement in the lounge at Maysan, LXR Doha
Maysan, LXR Doha Microdur Plus, sealed system, floors and walls throughout View the project →
Microrock microcement pool terrace at The OQ Hotel, Doha
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Related systems

Microcement A seamless mineral coating at 2 to 3 mm over a prepared substrate, sealed to a defined system. Microcement is durable and low-VOC. It is a cementitious product: specify it for wear, chemical exposure and continuity, not as a natural or breathable finish. Lime plaster A one-component hydraulic lime plaster with marble dust, laid by trowel at 1 to 4 mm over a prepared base. It carries the hardness and the standards record of a mineral coating while reading as a hand-worked surface — tadelakt, marmarino or polished plaster, depending on how it is finished.

Technical support for the design team

We supply the material and we apply it, so the specification and the workmanship sit with one party. Send a finishes schedule, an elevation or a mood board and we will come back with the system, the build-up, the sample programme and a completed clause.

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