Schmincke Aqua Drop is pigmented liquid watercolour that's available in 24 colours.
They are sold only in 30ml bottles. You can buy the colours individually or in sets. Shown above is the primary colour set that I bought from Jackson's Art (UK). The price is around £6 (US $7) per bottle which is quite competitive with Dr Ph Martin's Hydrus liquid watercolour which is also pigmented and available in 24 colours.
These are pigmented so it's best to shake them before use. Schmincke said these liquid watercolour can be used in markers, and for airbrushing. And they can be used together with tube or pan watercolour.
The colours that I have are Opaque White, Lemon Yellow (PY3), Magenta (PR122) and Cyan Blue (PB15:3).
The names used for the colours can be different from their Schmincke Horadam or Akademie watercolour products. For example, Magenta and Cyan Blue here uses PR122 and PB15:3 respectively while Horadam Aquarell Magenta uses PV42. Helio Cerulean uses PB15:3. So it's best to buy based on the pigment number rather than the name of the colour.
Only colour attributes available on the bottle are for the lightfast quality and transparency. There's no details on how staining the colours are.
I've tried lifting the colours here but it's difficult. The colours in this set are staining. There doesn't seem to be any non-staining or granulating colours from the list of 24 colours available. Burnt Sienna uses PBr25, Burnt Umber uses PG36 and PBr25, and there's no Ultramarine. Those three are very common non-staining granulating colours.
The black is deep black. You can add a tiny bit of water and you can get a dark black but still see pen and ink lines.
The bottles are made of plastic and they come with the useful eye dropper.
There are markings for 0.5ml and 1ml on the eye dropper but those can be difficult to see.
I find it more convenient to use a palette with small wells for these liquid watercolour, and a separate palette for mixing.
Here's a sketch I painted with the set of colours. The paper I've used is Fabriano 5 with 50% cotton content.
The colours are very vibrant and able to blend well. However, how well the paint can actually blend will really depend on the paper used.
The concentrated liquid watercolour is quite fluid, and can be diluted easily with water, just like typical tube or pan watercolour.
The colour mixing limitation for this set is warm orange as Lemon Yellow is a cool yellow. You can mix good skin tones with this set.
When you mix the three primary colours together, you can get a nice neutralised gray.
Glazing or layering works well, at least with the colours I have. These are very transparent watercolour and they work very much like ink.
The opaque white is quite opaque but you do have to go over it a second time to get 100% opacity.
The white is good for painting highlights.
You can also add white to the colours to lighten the colours and make them opaque.
I don't use liquid watercolour much so I don't know what they are best used for. Let me know in the comments section below if you do know.
The primary colour set is a good set for beginners to test the quality of the paint to see if this product can fit in your workflow, or if the product is suitable for the type of art you create. I guess these liquid watercolour are more suitable for detailed illustrations. They are incredibly staining so these are great for glazing. They are already in liquid form so it's easier to mix really large washes.
Disadvantage when compared to tube and pans would be portability. These bottles are best used indoors.
Overall, the quality of Schmincke Aqua Drop is excellent. They have a good selection of lightfast colours included but do beware of the ones with lower lightfast rating. It's always good to test your supplies before using them for professional art.
I recommend getting them from Jackson's Art (UK) as the pricing is competitive and shipping fees is quite reasonable. I bought my set from Jackson's Art.