Hot callusing pipe

Hot callusing pipes are used to bench graft difficult species during the winter. Pecan ,hazel walnut all respond to its use
OK. What is a hot callust with 2 inch plastic pipe .; Cut transverse slots into it about halfway through. A copper pipe sealed and filled with water having a heating cable attached to it is inserted into the pipe. You can not use the common roof cables or cables used to resist frost of water pipes. They have attached controls which cannot be removed. You need a separate control .
The idea is to provide heat to the graft only. The stock and any extending scion are exposed to cool temps. This is normally done in winter in a shed warm enough to avoid freezing but cool enough to maintain dormancy
There is much better info to be found on NNGA s web site Northern Nut Growers Association
My problem is getting a small amount of cable. Soil heating cable is a minimum 60 feet long I need only 6

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How about terrarium heating cable? 25ft = 50w. Just loop it back and forth a couple times.

Or here’s a 12’ soil cable for $29.95 that includes a 77-85 degree thermostat. Charley's Greenhouse & Garden Economy Heat Cable, 12 ft.


I did this exactly with a terrarium heating cable…mine is 25W, and I looped it up and down over and under the walnut graft union. They were tied with a rubber band, and nothing else, placed in a box with moist perlite covering the roots and graft union. 21 days later I checked them. This was my first try. One dead rootstock, two clear failures, others are showing some callus, but impossible to tell what the success rate is before spring. I take it they should be placed in a semi sheltered place, dappled light only, when the spring arrives?
Species is Juglans ailanthifolia, I am studying for heartnut grafts on local seedlings, practising for technique.

Few pictures from the ones that did form some callus.