If you have problems with joins then magic water alone or slip made with magic water or magic water slip made with paper pulp is worth a try.
You are adding sodium (from the sodium silicate plus the soda ash) which is a strong flux which helps fuse the joins together. Also, the silica in the sodium silicate adds a titch more glass former to the join. Sodium silicate is also really sticky stuff which helps the joint bond plus slip made with it dries really hard. It also acts as a defloc and is water soluble so is able to work into the surrounding clay a bit. So in theory the bond is stronger while drying right through to the finished join having more melt and fusing better when fired.