Metal is cold right? Well that is the perception that many people have, based on experience. For example, in the winter, even though the sun may be out in full force, why do you hesitate to grab the metal handrail as you go down a flight of stairs outside? That’s right; It is going to be “freezing cold”. Why is that?
To explain this, we need to speak briefly on the subject of thermal conductivity. Simply put, a steel handrail has 200 times the thermal conductivity as a plastic handrail. Which means that when exposed to cold, it get colder 200 times faster than if it were made of plastic.
So then, if you were to soak in a stainless steel tub, you will definitely not want to touch the metal because it will feel ice cold; Right? WRONG! (Sorry for the extra emphasis.)
The correct answer is that it will feel warm, especially when compared to soaking in your typical acrylic plastic tub. Why is this so? Once again, the answer has to do with thermal conductivity. If you keep your house at 72°F, that means that your tub is also at that temperature. Now let’s say you decide to soak in a warm bath. You fill the tub up with water that is 95°F. At this point, let us consider two scenarios:
[Scenario 1: Acrylic tub (typically bonded to a fiberglass structure)]
Once filled you get into your acrylic tub. The water feels great. Immediately, you place your arms on the ledge of the tub, and what do you notice? It feels cold. Yuck! Get your arms back into the warm water.
[Scenario 2: Stainless steel tub]
Once filled you get into your stainless steel tub. The water feels great. Immediately, you place your arms on the ledge of the tub, and what do you notice? It feels fairly warm.
Why is this the case?
Well, stainless steel has a thermal conductivity rating of about 16. Acrylic/fiberglass has a rating of about 0.1. This means that the stainless steel tub warms up 160 times faster than the acrylic one. In practical use, before you get into that stainless steel tub that you have just filled with nice, warm water, the tub itself has already warmed up due to heat transference from the water to the metal. Even the parts of the tub that are not in direct contact with the water will quickly warm up as well. In the case of the acrylic tub, it absorbs heat so slowly from the water, that any area of the tub that is not in direct contact with the warm water will essentially never warm up.
Does this mean that the stainless steel tub filled with warm water will cool off faster than the acrylic one?
It might, but were it not for insulation. In the case of DaVinci Spas, we insulate the stainless steel tub shell with a high-tech material that serves as a thermal barrier, reflecting all of the heat back towards the water.
In conclusion, if you want to enjoy a comfortable soak in a tub, first, have the vessel designed by DaVinci Spas to fit your body, and soaking position preference, and second, have it made from stainless steel. It will be the best soak you’ve ever had.