The purple haze is most likely a color cast and flare/reflection issue from the welder’s glass, not something an ordinary UV or IR-cut filter will fully fix. Welder’s glass usually isn’t optically neutral, and its flat surfaces can add internal reflections.

For this kind of shot, use proper optical-quality filtration instead: a dedicated solar filter or very strong neutral density filters. If IR contamination is contributing to color shifts, an IRND filter can help control that, but it’s not a substitute for the main light reduction needed, and it may not address heat concerns.

A safer, more flexible approach is often to shoot a series of shorter exposures and stack them rather than leaving the camera pointed at the sun for one hour continuously.

So: avoid welder’s glass for image quality, use purpose-made optical filters, and consider stacking short exposures instead of one extremely long exposure.