I already knew that HVLP and airless spraying were different to each other. With my airless sprayer, you have to select the correct tip size for the job in hand and typically do not need to 'thin' or 'reduce' the material being sprayed in any way at all. With HVLP, you have needles and air cap combinations, instead of tips and tip guards. That in itself is simple enough, once you get your head around it and understand which needle size goes with which type of product you are spraying.
What was somewhat new to me with HVLP, was the concept of thinning the product to be sprayed. I had read on many forums that adding 10% water (to a water-based product), was the way to go. Without further a do, I jumped in with the 10% dilution theory and had somewhat less that impressive results!
With my HVLP setup came a viscosity cup, which I had also read up on, but had not used. Back to basics me thought and I resorted to timing my product through the cup for the first time. The 'suggested' time for the material to pass through the cup was in the 40 second region. On the first pass, the material took over 3 minutes (that's more than 180 seconds), which was way too viscous / thick - no wonder I had problems with the initial run.
Adding 10% water (as suggested elsewhere), the time through the cup was reduced to about 2 minutes, so it was heading in the right direction, but nowhere near enough. Elsewhere, I had read that temperature had quite an influence on the viscosity of the paint and as I didn't want to go mad with adding too much water, I decided to run a bowl of hot water from the tap and stood a container of undiluted paint (measured so as to keep an eye on the %'s correctly) in said hot water. I stirred the paint in it's container, stood in the hot water for about 5 minutes. I then re-timed the paint through the viscosity cup. The increase in temperature had a similar, if not slightly greater, influence on the paint, compared to the water. It now went through in less that 2 minutes (remember, this had no dilution at this point!).
Still somewhat off of the target 40(ish) seconds, I now began to add 10% water and then added more water in 5% increments. After what seemed an age (about 20 minutes!), I had the paint running through the cup in 40 (or thereabouts) seconds - this was good enough for me. 15% with one product and 20% with another product - the 10% rule has not worked for me thus far.
What a difference this made. I was AMAZED at how much better the same product now came out of the spray gun and how much better it was laying out on the target surface. Hey presto, I think I have sussed it!
I will be making note of the timings for each product alongside the % dilution as I go along. I can see the viscosity cup and I are going to be friends for a while to come until such times I have this nailed instinctively.