Hi @LouiseFraser,
Welcome to the Bunnings Workshop community, it is wonderful to have you with us.
The key difference between Sikkens Cetol HLSe and Sikkens Cetol BLX Pro is that HLSe is oil-based and BLX Pro is water-based, and that drives how each performs on pine in full sun.
Water-based stains like Sikkens Cetol BLX-Pro are easier and faster to apply, but they rely more on surface protection. They dry quickly, clean up with water, and have lower odour, but they do not penetrate as deeply as oil-based products. In full sun, this usually means they break down sooner and need recoating more often.
Oil-based stains like Sikkens Cetol HLSe Timber Finish penetrate deeply into pine, bonding within the timber rather than just sitting on the surface. This deeper penetration gives better adhesion, copes well with timber movement, and provides a more stable base against UV breakdown over time. In exposed conditions, oil-based stains generally weather more gradually and are less likely to fail suddenly, which helps extend the time between maintenance coats. In saying this, they dry slower and are tougher to clean up if spills happen, but in terms of UV protection, they will be more durable.
HLSe can be used as a standalone product, with 3 coats being applied, or as a base coat that is topped by 2 coats of Sikkens Cetol Filter 7 Plus. HLSe is a penetrating oil-based stain, so its strength is soaking into the pine, locking into the fibres, and providing a stable, well-bonded foundation. Filter 7 is designed to sit on top of that penetrated base and add a tougher, more UV-resistant protective layer.
For a pine pergola that is fully exposed year-round, an oil-based system like HLSe, especially when used as a base coat before applying Filter 7 Plus, will typically last longer and provide better long-term UV protection than a water-based alternative.
Let me know what you think and if you have further quetions, please don't hesitate to ask.
Jacob
