I wanted to comment on using the sodium silicate in the radiator. First off, I have never tried it in any radiator but I do know it will seal leaks.
We use it extensively in plastic injection mold cooling lines. The mold steels we use vary from pourous non ferrous metal castings like Beryllium Copper, Meehinite, Kirksite or Aluminum to hardened and pre-hardened forged tool steels such as P-20, 4130, 420SS, H-13, A-2, D-2, O-1 etc. Occasionally the water passages will develop leaks from small cracks from millions of heating and cooling cycles. We use sodium silicate to re-seal them. We have to pre-heat the metal to just under 200°F and introduce the solution under pressure for about 2 hours. It sticks to EVERYTHING, sealing the leak and leaving a thin film that hardens around the perimeter of ALL water passages. In taking thermal readings to determine the resultant thermal conductivity of treated metals there is a difference in heating and cooling cycles of the metal inserts. In each case, their thermal conductivity properties have been compromised by the sodium silicate and no longer respond to the faster heating and cooling cycles as before. This is due to the "water glass" effect, the coating of the water passages. This is extremely important when costing out piece price. These molds run millions of cycles and a one penny on a $1 piece (1%) can make a huge difference when considering if it makes 10 million cycles per year or 11 million. And this is for only ONE injection mold. For example, if the mold is a 32 cavity mold, the additional 1 million cycles will produce 32 million more parts per year....do the math. If you have a hundred molds running, it becomes astronomical.
Now I don't think it will plug up radiators as stated above, but I do know that there will be a film of it adhered to the internals of the radiator and will definitely have an effect on it's performance ....whether measurable or not. How much?...I don't know, but it will. ?? Or will it make a difference on the engine's ability to operate... probably not significant enough to worry about. Of course, that's why we use it in our plastic injection molds even though we know the results. In that respect it may be similar to Barr's except that it does not plug up radiators as stated about Barr's but I don't know because I've never used that either.