Providing adequate steam supply is important when steaming for color, but ESSENTIAL when you are shock steaming. When you are shock steaming your objective is to reach a certain internal wood temperature as soon as possible and return the lumber to normal temperatures again without any (or miminum) color change or degrade. If the steam chamber is unable to reach the desired temperature in a short period the lumber will begin to change color or generate degrade, which is exactly what the we are trying to prevent.
Steam supply requirement.
Steam pressure requirement.
Low pressure steam is the best, since it is not as overheated as high pressure steam, when released into the near zero pressure environment of the steam chamber. The high pressure steam will create more heat with less moisture added to the air, which will result in a lower relative humidity. Higher relative humidity help prevent degrade.
Metric: Best steam supply pressure is 0.5 bar (mainimum 2-3 bar).
Imperial: Best steam supply pressure is 8 psi (maximum 30-45psi).
Steam volume requirement.
As mentioned earlier steam volume is important (especially when shock steaming) for insuring a good steaming result. The amount of steam you can supply the steam chamber is nearly directly related to the time it take reach your final steam treatment temperature. Simply put more steam input equals more energy released into the chamber for heating the lumber.
More steam supply = shorter heating period.
Metric: Rule of thumb: Minimum 60 kg steam/hour per cubic meter of lumber.
Imperial: Rule of thumb: Minimum 300 lbs steam/hour per 1000 boardfeet of lumber.
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