Sikkens TS Interior substitute?

My internal Vic Ash window sills are finished with an unknown brand of water-based clear. I asked the painter to use it because I wanted a non-yellowing finish. It met that requirement nicely, but unfortunately quickly became damaged due to condensation pooling on the sills. I've now solved the condensation problem with dehumidifiers and I wan't to refinish the sills.

A few years ago I refinished a couple of the sills with Sikkens TSI. It's a satin, oil-based, thixotropic (gel) finish. I love the stuff because it doesn't drip off the brush and doesn't leave brush marks, because it doesn't set-up too quickly like some polys (e.g. Estapol). It also doesn't have a plastic look when dry like some polys. And it doesn't seem to be as yellow as the run-of-the-mill PUs either. Although that could be my imagination.

Anyway, Sikkens are no longer importing Cetol TSI into Oz. My only experience with clear polys has been Estapol, Feast Watson Satinproof and the Cetol TSI. I don't like the way the Estapol or Satinproof goes on, nor do I like the look of them.

Can anyone recommend a similar finish to the TSI? Cost isn't an issue as I won't be needing much.

TIA.

What is the timber that it yellows? Have you considered using a natural penetrating oil instead? Once it becomes dry, you only need a few drops to nourish the surface again. Easy done.

Hi Angela,
The timber is Victorian Ash. I’ve never heard of penetrating oils being used on window sills. Have you tried this?