Watco 4 Hour Epoxy Primer


A 2-component primer for porous, bare, concrete, sand and cement screeds, bricks and blockwork that is ready to be over coated in only 4 hours.

  • For priming bare, porous, or open textured surfaces prior to applying a high build floor finish
  • Ready to be over coated in only 4 hours
  • Virtually solvent free two pack epoxy resin – safe for use in confined areas
  • Binds weak and friable surfaces
  • 100% solids epoxy offers major benefits over traditional water-based primers – highly penetrative, exceptional binding and strengthening properties and rapid curing

Note: While great care is taken with the colour samples shown, no guarantee can be given that they represent exactly the colours offered.

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£109.00(ex. VAT)
£130.80 (inc. VAT)
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Watco 4-Hour Epoxy Primer prevents ‘air entrapment’ bubbles forming when high build coatings are applied to open textured surfaces. It is a highly penetrative, two pack, virtually solvent free primer, especially designed to reduce the porosity of bare, porous, or open textured concrete and high suction floors.

Watco 4-Hour Epoxy Primer also binds together and strengthens weak and friable surfaces ready for painting and it offers significant benefits over traditional water-based primers; not only because of its exceptional binding properties but also how deeply it penetrates into the substrate and how rapidly it cures. This rapid curing, high performance formulation allows the floor to be primed and coated in the same day.

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Features & Benefits

  • For priming bare, porous, or open textured surfaces prior to applying a high build floor finish
  • Porous, bare, concrete, sand & cement screeds, bricks, and blockwork.
    • The moisture content of concrete should be less than 75% RH.
  • Ready to be over coated in only 4 hours
  • Virtually solvent free two pack epoxy resin – safe for use in confined areas
  • Binds weak and friable surfaces
  • 100% solids epoxy offers major benefits over traditional water-based primers – highly penetrative, exceptional binding and strengthening properties and rapid curing

Surface Preparation

Bare concrete – remove surface laitance, dust and any light dirt or grease deposits using Watco Etch & Clean. Flush with clean water and allow the surface to dry thoroughly and for as long as possible to allow Watco 4-Hour Epoxy Primer to penetrate. For the removal of heavier deposits of oil and grease we recommend Watco Concroff, again, flush with clean water and allow the surface to dry thoroughly.

New concrete – as a guide, new concrete should be left for eight weeks to dry. The surface should then be prepared using Watco Etch & Clean and thoroughly rinsed away and left to dry prior to using Watco 4-Hour Epoxy Primer.


Remove the two inner tins from the tall outer tin. Stir the contents of each tin thoroughly and pour all of the contents into the outer tin (scrape around the inside of the tins to remove any residue). Mix the components together thoroughly using a spatula or similar wide bladed tool (a piece of wooden batten is ideal). Continue mixing until an even colour and consistency are obtained. Do not mix more than one pack at a time. If a paint stirrer fitted to an electric drill is used, also use the spatula to blend in any unmixed material from the sides and bottom of the tin.


Important – once the contents of the pack have been mixed, a chemical reaction takes place which creates heat, and the product should therefore be used immediately.

Best results are obtained in warm (minimum of 15°C), dry conditions with good ventilation. Apply one coat with a medium pile roller, (not foam), working well into the surface of the concrete.

Do not exceed the maximum coverage rate (see section headed ‘Coverage’ for further information).

As a guide, Watco 4-Hour Epoxy Primer can be over coated with a high build coating when it is touch dry (generally 4 – 8 hours) but should be applied within 48 hours. If more than 48 hours elapse, the primer should be lightly abraded to provide a key.

Test Results

  • Abrasion Resistance ISO 5470-1 - 147mg
  • Flexibility ISO 1519 - 2mm
  • Adhesion Test EN 1542 - 2.8MPa/Nmm2
  • Water Permeability EN 1062-3

Case Studies

Paradise Wildlife Park, Hertfordshire - primed the surface of their lion enclosure before overcoating with an ultra-hard-wearing topcoat to withstand the wear and tear of the area, whilst also having the ability to tolerate lion urine.

Commercial vehicle servicing and repair company in Cardiff - new floor installed in their workshop, which would inevitably be subject to oil ingress and heavy wear and tear. Initially the surface was primed with 4 Hour Epoxy Primer, then after 24 hours it was given one coat of Epoxicote High Build

Product Details

Data sheet

For Use By
Professional Use
Interior / Exterior Use
Water / Solvent Based
Application Method
Medium pile roller
Cut in using a brush
Pack Size
Minimum Applied Thickness
250 microns
Mixing Ratio
100 parts resin : 50 parts curing agent.
Key Features
Intended for use prior to applying a high build coating. If the top coating is anything other than high build, please contact us for further advice
Key Features
Do not apply to a damp surface since 4-Hour Epoxy Primer relies upon penetration.
Approx. values:
Smooth concrete – 20m2 per 5 litres
Acid etched concrete – 15m2 per 5 litres
Shot blasted/open textured concrete – 12.5m2 per 5 litres
Recommended Thinner/Cleaner
It is not practical to clean applicators and they should be discarded after use.
Min. Application Temperature
Air temperature 15°C
Floor temperature 10°C
Recommended Dry Film Thickness
250 microns
Recommended Wet Film Thickness
250 microns
UN Number (Activator)
UN Number (Base)
Pot Life
Up to 20 minutes at 20°C
Up to 30 minutes at 15°C
Base Type
Exterior / Interior Use
Interior Use
Suitable For Use On
Suitable For Use On
Suitable For Use On
Suitable For Use On
Suitable For Use On
Sand and Cement
Application Method
Product Type
Maximum Overcoating Time
48 hours
Minimum Overcoating Time
4 hours
Colour Family

Customer agrees that before placing an Order, Customer has read and understood the most up to date Product Data Sheet for the Product. Where we have access to the Product Data Sheet from the manufacturer, we will either provide a copy on request, or include a link to the Product Data Sheet available on the manufacturer’s website. Customer further agrees that we have no liability for any errors or omissions contained within the Product Data Sheets. For more information, please see our Terms & Conditions of Sale.

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Watco 4 Hour Epoxy Primer is only available with the shipping and delivery timescales listed below - please do not contact our Customer Support Team with enquiries about alternative or earlier shipping and delivery times.

Saturdays and Sundays, as well as Bank Holidays, are not classed as working days.

Orders placed after the cut-off for this product will not be processed for earliest dispatch until 9am the next working day.

All delivery costs below are excluding VAT

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*All estimates are based on theoretical consumption rates for a single coat and do not take into account any substrate deviations or wastage


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