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Cybers How to build a bulk steam pasteurizing unit

Steam Pasteurization

So, you will need

some 1/2" PVC pipe
1 1/2" T pvc fitting
2 1/2" PVD end caps
A Wagner 705 Steamer (Homedepot in the paint section, used for removing wallpaper)
1 LARGE rubbermade tub
1 Wire shelf to fit the tub
1 meat thermometer
Extra fittings to fit the 1/2" PVC to the Wagner unit. (Not an exact fit, just get it as best you can)

This is the Rubbermade

The Wagner Power Steamer

The Shelf

These are the extra fittings that I came up with to fit the Wagner Power Steamer to the PVC pipe

You will also need
A drill, dremel tool, knife, and I used some silicon sealant but it really did not work that well.

We start by cutting 4 pieces of PVC 5" long These are the supports used to hold the wire shelf off the bottom of the rubbermade.

I then used the dremel tool to notch the end of them so that the wire shelf would sit into the notch and hold them in place.

You will want to cut the PVC so that it is almost as long as the rubbermade and use the fittings to make a T shape. This is to distribute the steam evenly in the unit

Then you will drill holes in the PVC for the steam to come out.

This is the PVC T and the standoffs in the rubbermade. So you can see how I laid them out.

Using a sharp knife I cut a hole in the bottom of the rubbermade, about center, for the 1/2" PVC to pass through.

Here is a shot from the top with the PVC-T in place, as well as the standoffs, and Shelf

I then Push the Adapter onto the pcv and using silicon fill in the hole where the pipe comes through.
NOTE: The Silicon did not stick will and broke loose when I tested the unit. However, it does provide a little bit of a gasket effect around the hole so there is no harm in having it there but I would not consider it needed.

The Silicon

This is a shot if the unit assembled

Taking the drill I drilled a small hole in the top of the rubermade and pushed the meat thermometer through the hole. This way I can see what the temp is inside the unit.

Once everything was dry I attached the hose from the Wagner power steamer to the unit.

I power up the Wagner power steamer and let it run for a while then open the box and check

After 30 min the unit came up to temp

Note: this was the temp running it empty, It should run a little warmer than that once it is full because the stuff being pasteurized will retain heat and help to raise the temp. However 165f is in the pasteurization range so all looks good!

To use the unit Make up your Substrate or Casing layer using your own recipe. Load it into pillow cases and put the pillow cases into the unit. Fill the Wagner Power Steamer with water and turn it on. Wait for the inside temp to reach 161f then start your timer. 2 hours between 161f and 170f is perfect to pasteurize the material for use.

I have found several references including one from the agricultural Sciences department at penn state that list steam pasteurization temps for substrate at 60c-70c (140f to 158f) which is lower than the 160f to 180f that I have seen many on the board suggest.
It may be that the difference comes from the difference of hot water pasteurization vs steam pasteurization as most commercial grows use steam pasteurization where as most of the people
on the board use a hot water pasteurization.

The First Run with the unit
100lbs of substrate
30min to start steaming
60 min to come up to temp (71c)
Added more water at 2hours from start, Temp dropped 12c during the time it took to add the water.
15 min to start steaming, total temp drop 24c
10 min to return to (71c)
2 1/2 hours at 71c

Note, you should get the high temp PVC, I used the standard PVC and it appears that it can not handle the heat. I will be replacing it before my next run.


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