The Brew Cabin

Good afternoon and congrats on a fine site.
I wonder if you can offer any help.
I have recently laid a patio, and grouted such over a 2 day weekend. However, although i was sure i mixed the same ratios for the grouting over the 2 day period, in reality i now have a patio area which has two completely different coloured mortars.
Are there any products i can purchase to stain the two different colours to make one uniform one, or can it be done with a very watery sand / cement mix, painted with a paintbrush ??

Any advice would be grateful.

As far as i know there is no easy solution to your problem as all the mortar stains i have come across are either mixed with the sand and cement before laying or are a powder that has to be added over the concrete soon after laying and then sealed in, but i may stand corrected.

Nope, you're right Alan. Once the mortar has been coloured and the cement has set, then the colour is fixed. There are no retro-colouring options.

Perhaps this is an opportunity to extol the virtues of pre-mixed coloured mortars, which ensure shade consistency, but, to be fair, these are only really available in industrial quantities, although a black lime mortar is available in 40kg bags, if you know where to look.

For the average patio job, then batch control is essential. If there is any variation in the sand being used, the brand of cement, the brand of dye, the type of additioves/plasticisers/waterproofers, or quantities of any of these, then the shade can, and probably bloody will, come out all different! :(

As for poor Warren with the mis-matched mortar, the only real option is to use a nangle grinder or power saw to nick out the top 12mm or so of the existing mortar and re-point the lot, in one go, with a carefully batched mortar. I don't envy you!

Alternatively, you can ignore it for the rest of the summer and by next spring, you'll not even be able to tell the two batches don't match. :)