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</o:shapelayout></xml><![endif]--></head><body lang=EN-ZA link="#0563C1" vlink="#954F72" style='word-wrap:break-word'><div class=WordSection1><p class=MsoNormal><span style='mso-fareast-language:EN-US'>Hi good folks<br>has anyone got experience with making up one’s own traditional burnt sand mastic for caulking around openings and for providing a flexible seal for expansion jointing between different materials.<o:p></o:p></span></p><p class=MsoNormal><span style='mso-fareast-language:EN-US'><br>Down South here in South Africa we only get conventional silicone or polyurethane type joint sealers/caulking agents, which are environmentally dodgy and unsuitable for natural finishes. I gather that people in the UK and US are using a traditional burnt sand mastic with certain suppliers selling it as a product.<br><br>As far as I can tell, you can make your own by roasting or baking a fine sharp sand to sterilize and drive off all moisture and then about an hour before use one blends it with a high quality boiled or double boiled linseed oil. It seems some caulk may also be added to the sand mix, but I am not sure if this is required or not. <br>I was also wondering if you could sun-cure a raw linseed oil rather than use the boiled type in the same way one sun-cures linseed oil for an earthen floor.<br><br>Can anyone advise?<br>It would be interesting to hear people’s experiences. <br><br><o:p></o:p></span></p><p class=MsoNormal><span style='mso-fareast-language:EN-US'>Many thanks <br><br>Best regards<br>Andy Horn<o:p></o:p></span></p></div></body></html>