Powdered burnt clay is called surkhi, it may be made using burnt bricks, burnt clay tiles or simply prepared by burning the right kind of clayey soil. Surkhi is what makes lime into ‘lime’. Without surkhi, lime is only good for limewash. Lime and surkhi come together to make a homogeneous mix. Jaggery and fenugreek seed water is added to this mostly when doing roofs or repairing cracks. Jaggery is sticky, enhances binding and keeps moisture intact preventing sudden drying and hence preventing cracks. Methi gives workability and adds to the waterproofing quality of the surkhi mix. In a mortar, the jaggery holds two bricks together tightly. For plaster, it is unnecessary to add jaggery. If you add it to the plaster, the consistency will change and will not give the desired result the mix will become and lose and take longer to set.