A thick report about 2 cm long was sent to me by Professor Kamada of Jissen Women's University who studied the heat retention of wet suits and wrote a report. So, I didn't like letters very much, and I read only a thin report (PDF) summarizing the report, but for the thin report, the heat retention of the wetsuit is different in various materials, for example. It was written that the effect of the difference between jersey, far infrared rays, and titanium knitting was only a few percent. Wetsuits rubber makers are still making and releasing new products, but the research team at this university has spent about three years researching them, and the top and bottom water that surfers use. It made it clear what the best heat retention of rubber is when you are immersed in it. The thin report concludes that the heat retention of rubber depends on the thickness of the rubber. I believe in that report and use it to make wetsuits, but when I try it on, it certainly is. Even 0.5mm is warm if the rubber is thick.

However, I didn't read the thick report at all, and when I read it again recently, it said that it was the beginning of a wetsuit. National Rubber, a rubber company that I still use, said that National Rubber first manufactured neoprene rubber with closed cells in 1959. So in 1960, we started selling wetsuits for diving using neoprene rubber. Naturally, the wetsuit probably started to be manufactured by buying fabric from National Rubber. That was the 1960 wetsuit for diving. So, when I started surfing, my seniors wore skin-type rubber on the back and front, and maybe a plain neoprene rubber diving wetsuit made by National Rubber, at that time. I think divers still do, but I used to put powder inside and take off and put on the wetsuit in a warm bath to adjust the ease of wearing the wetsuit. (to be continued)