It’s been a few years since I shot wet plate (I miss it) however when I first set up to do portraits in wet plate I bought two large LED lights and it was a pretty miserable experience. They simply don’t put out enough UV light for wet plate. I returned the lights and bought two large flurencent lights and it worked much better. I got my exposures below 20 seconds but it was a lot of light on my models. It was difficult for them to look natural and not squint.

Unfortunately the company that made the ones I bought, Fotodiox, stopped making the ones I bought. But you can see them on this link to Amazon. Maybe that will give you an idea for one to build.

-Joshua