Application of the colour is most commonly done via the broadcast method, where handfuls of t
he colour hardener is thrown over the surface, keeping your hands low as if the colour is being rolled on. Other methods include using an applicator, similar to a colander and shaking over the surface, this can be difficult to get adequate coverage in areas further from the edge.
The colour is usually despatched in bags, the weight and coverage rates should be checked prior, to ensure you have sufficient coverage for the size of the job. Using less than the recommended amount will detract from the strengthening properties of the product, not to mention the final look. Coverage rates can be affected by the weather and also surface water if the concrete. The timing of the application of the colour is critical, apply too soon and the colour will be eaten up by the concrete, too late and you will not be able to trowel it into the surface. When the colour hits the surface of the concrete it will darken, keep applying in layers until the you see the colour stay light. Test by running a steel pool trowel over a treated area, should the grey of the concrete show through, more colour is to be applied.
The whole are should then be trowelled to a smooth finish using a pool trowel and a fresno, also ensure all grids, manholes, shuttered edges etc. are bullnosed using a radius edging trowel.
Ensure you are purchasing a colour hardener, not just a dry shake colour, the difference being that the colour hardener will make the surface tension much greater, so that when the surface is imprinted it will not wear. Any dry shake powder without a hardener in it relies on the concrete to absorb it and colour the surface giving it very little extra surface strength required to pattern the concrete. If in doubt always ask for a copy of the test certificate for the colour hardener, any good supplier should have one to hand.