In a saucepan, pour in 170ml (the rest) of the water. On top of the water, pour the granulated sugar, golden syrupand the pinch of salt. Do not stir. Bring to a rapid boil until the mixture has reached a temperature of 120ºc. This should take around 15 minutes, keep an eye on it as you don't want to to burn.
Keep a pastry brush and a small bowl of water handy. Carefully brush water around the inside of the sauce pan to create condensation which will prevent crystals from forming.
Once the sugar mixture has come to temperature, take it off the heat.