Determine the building specification ratio of a recommended mortar mix. If it calls for a 1:3 ratio, then you will add the 2 numbers together and divide the result into 38, to determine how many bags of cement. After you have mixed soft and sharp sand with lime together, form a circle with the mixture and the hollow the centre out. Next, shovel or tip in the required amount of cement. Then mix them all up together shovelling them towards the centre. When the mixture is one uniform colour, you will hollow out the centre once again and tip water into the centre start with ½ a bucket. Mix everything into the middle once more and keep turning it over until the whole mixture is even in colour and consistency.