Description :

The original mastic for junctions between masonry, render and wooden windows and doors, also used extensively for leaded or metal framed windows up and down the length and breadth of the United Kingdom and Ireland for at least 200 years, Burnt Sand Mastic fell out of favour because it required site mixing.
The emerging DIY market developed more user friendly, but actually significantly less durable of the shelf products with a much shorter life span, an often-repeated short term solution, now clearly recognised as ineffectual and not fit for purpose without constant maintenance. Traditional windows that are set behind a masonry rebate are not fixed in any way to the outside
masonry; rather they are wedged and held from the inside by battens for lath and plaster or plaster on the hard with plaster straight into the woodwork or by window shutters, in all cases the actual window frames are free They were often face bedded around the frames with hairy lime plaster to ensure full contact with the rebated masonry detail, and subsequently pointed up externally with Burnt Sand Mastic to form a long lasting, completely wind and water tight flexible joint between the outside masonry and the timber frame. This method of fitting timber frames to openings in traditional masonry buildings has never been surpassed and should not be altered. Traditional Burnt Sand Mastic Made by roasting sand on a hot plate or in a kiln and was originally mixed with lead-based driers and crushed chalk. However, for many decades now, alternative natural driers have replaced the lead
products. Burnt Sand Mastic is available in a limited number of colours by request. Masons Mortar Ltd Burnt Sand Mastic as supplied, contains no lead products. New installations should follow traditional practice. Repair work may have to take account of erosion As supplied Burnt Sand Mastic is a two-part product, the burnt sand, in a tub and the two part oil and drier in a plastic bottle. For each litre of burnt sand add approximately 200 millilitres of oil hardener. This is best added a little at a time, ideally let the sand sit in about 2/3rds of the oil required until it is absorbed fully, and mixing occasionally to ensure all the oil is absorbed evenly. This is best done at least a couple of hours ahead of with the final addition of oil drier added with vigorous mixing. Mastic should drop cleanly of the mixing trowel. – it is not a mortar like consistency, it is pushed into gaps from a mastic box.