Do not do it.

There are numerous hot tear tests, nearly all of which are not helpful. This is the result of experimenters not realising that the key ingredient to initiate a hot tear is a bifilm. Thus the awful designs of filling systems used for these tests ensure a dreadful contamination of bifilms in the liquid alloy which encourages the hot tearing behaviour, although the random changes to the pouring procedure and the quality of the incoming metal ensures that the results of all such hot tearing tests are highly scattered.

If a good filling system were to be designed on to all hot tearing tests, and if the metal quality of the melt to be tested were good, no suitable bifilm would be present (I assume a population of minute bifilms would be always present, but these would be too small to have any significant effect) so that no hot tearing would be observed.

I have always managed to cure hot tearing problems in castings on the shop floors of foundries not by reducing the strength of cores to reduce stresses in the solidifying casting (which is the traditional approach), but simply by improving the filling system design to avoid turbulence during the pour.

At the university, the experience I had with the ring test, in which a ring-shaped casting is formed around a cylindrical steel core was an instructive example. This test is a severe hot tearing test for metal pouring into the open top of the ring since the steel core in the centre of the ring provides a condition of maximum stress during the cooling and contraction of the casting. The total length of cracks in the ring is a measure of the hot tearing tendency. Numbers such as 50 to 150 mm are typical crack length values for the high strength, highly hot tear susceptible alloy A201 (Al-5.5Cu-0.7Ag).

Instead of top pouring of the rings, I arranged for my student to fill the ring with this difficult alloy via a bottom gate, via a fine filter to take out the major bifilms. He arrived with his result: a set of four castings so tightly contracted on to the steel cores that they could not be separated. Yet the castings had zero cracks. This was an example of the world's most severe hot tearing test with one of the world's most hot tear susceptible alloys, but with zero hot tears.

I was amazed and speechless at this unbelievably good result as predicted.

I always impressed at the reaction  of my student who sat there impassively viewing his perfect castings, and said: "Yes. A complete failure". "What?" I gasped, hardly believing my ears. "Yes" he said, "A hot tear test which does not hot tear."

If you like, you can find out more about bifilm defects, and how they control the properties of castings and cast products, from my books and publications, especially my latest effort "Complete Casting Handbook".   I wish you well.