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So I've been planning on moving my paints into dropper bottles and I've been watching a few videos on the subject for ideas and one thing I've noticed is that some use water and others use flow aid (eg lahmaine medium) during the latter stage when cleaning out the last of the paint from the pot in order to help agitate and get the paint flowing.

Now water I get, it thins the paint and shouldn't have any lasting effect nor be any long term problem since I'm likely to add some water to thin paint when using it normally. However I was under the impression that flow-aid liquids adjust the properties of paint a little bit differently to water. Water just thins whilst flow aids tend to make the paint more see-through to a slight degree. Is it simply that a small squirt of flow aid in a whole paint pot of paint has little to not discernible effect (ergo its too little) or is this a mistake some are making and not appreciating the difference.

Do both. You're effectively making your own layer paint.

The Allfather wrote:
Do both. You're effectively making your own layer paint.

Aye but when its already layer paint? ; )

Flow-aid and Lahmian Medium are really different things though. Flow-aid is added to water and reduces the paint's surface tension. Lahmian Medium is exactly that, it's matte medium, so it is a binder. It might have some sort of flow-aid in it, I don't know, but it isn't the same and will change the transparency of the paint, as noted.

 H wrote:
Flow-aid and Lahmian Medium are really different things though. Flow-aid is added to water and reduces the paint's surface tension. Lahmian Medium is exactly that, it's matte medium, so it is a binder. It might have some sort of flow-aid in it, I don't know, but it isn't the same and will change the transparency of the paint, as noted.

Ahh that makes more sense! I'd seen the videos using all three and I believe one mentioned using flow aid or medium interchangeably. Flow aid sounds like it would work rather like water then, just without any impurities.

 Overread wrote:
Ahh that makes more sense! I'd seen the videos using all three and I believe one mentioned using flow aid or medium interchangeably. Flow aid sounds like it would work rather like water then, just without any impurities.

Yeah, but you don't want to go too hard on pure flow-aid, or the paint will lose so much cohesion it will really be a total mess. I use Liqitex flow-aid and the bottle recommends (IIRC) a 1:10 ratio of itself to water. That is likely about right, but you've got some wiggle room. I've accidentally put pure flow-aid into paints before though and it's a disaster, the paint is basically unusable at that point.

Water is actually quite 'sticky' in the grand scheme of liquids; it has quite a bit of surface tension. Flow aid makes water a lot more runny.

In terms of affecting the properties of the paint, water will have the least impact. Water-based acrylics have water in them anyway (obviously), and if you add too much water, you can leave the the paint uncovered for a 10-20 minutes or so and some will evaporate out.

Adding flow-aid will fundamentally change the properties of the paint, so in my opinion, it doesn't make sense to use it when you are decanting paints.

I've decanted a lot of GW stuff into dropper bottles and I've just used water, absolutely no issues. I do use bottled water just to be safe though, limescaley old pipes around where i live

Both water and medium help getting the paint to flow better. There seems to be a general notion that addition of mediums "changes the properties of the paint" (with implications at chemical levels)... As someone who has been painting (watercolor, oil, acrylic, tempera) since 5 years old... I can attest that water is not this evil magical liquid that changes water-based paint.

It's important to note that every medium/flow improver, including plain old water, are simply just different types of solvents.

Now, how do these different solvents actually differ? Depending on the composition of the solvents, it can make paint dry faster/slower, make it more opaque/translucent, make it more sticky/loose, etc. What does this mean? Depending on how you've altered the nature of the paint, you end up with different results (whether they be drastic or minute)! None of these solvents CHEMICALLY CHANGE THE COMPOSITION OF THE PAINT & ITS PIGMENT. I feel like people really need to understand this instead of feeding others false information.

And just as a note - the word 'decant' is actually being misused here.

Some people also suggest minieral spirits. No idea what that is myself.

The Allfather wrote:
Some people also suggest minieral spirits. No idea what that is myself.

It's just a non-polar solvent in this case. Essentially it will just thin the paint. It's likely complete overkill though, I've put a bunch of GW paints into dropper bottles and all I used was water, flow-aid and a tiny bit of airbrush thinner (for the thickest of them).

 skchsan wrote:
Both water and medium help getting the paint to flow better. There seems to be a general notion that addition of mediums "changes the properties of the paint" (with implications at chemical levels)... As someone who has been painting (watercolor, oil, acrylic, tempera) since 5 years old... I can attest that water is not this evil magical liquid that changes water-based paint.

It's important to note that every medium/flow improver, including plain old water, are simply just different types of solvents.

Now, how do these different solvents actually differ? Depending on the composition of the solvents, it can make paint dry faster/slower, make it more opaque/translucent, make it more sticky/loose, etc. What does this mean? Depending on how you've altered the nature of the paint, you end up with different results (whether they be drastic or minute)! None of these solvents CHEMICALLY CHANGE THE COMPOSITION OF THE PAINT & ITS PIGMENT. I feel like people really need to understand this instead of feeding others false information.

And just as a note - the word 'decant' is actually being misused here.

An issue of wording on my part: the point I was trying to make was that, once you add a non-water medium into a paint, you can't get it back out. Assuming the only medium in the paint to begin with was water (which is the case as far as I know for GW non-wash paints?) then adding another medium will change the composition of the paint irreversibly, whether or not anything chemical happens. (Also speaking from years of Gouach/ Acrylic/ Oil/ etc. Experience here)

shmvo wrote:
An issue of wording on my part: the point I was trying to make was that, once you add a non-water medium into a paint, you can't get it back out. Assuming the only medium in the paint to begin with was water (which is the case as far as I know for GW non-wash paints?) then adding another medium will change the composition of the paint irreversibly, whether or not anything chemical happens. (Also speaking from years of Gouach/ Acrylic/ Oil/ etc. Experience here)

It seems like a lot of terms are getting jumbled up here.

All acrylic paints have an acrylic medium, usually matte, in it. Then they also likely have some amount of added water or other solvents to dilute/thin it.

Although you are right, if you add more medium, you can't take it back out. If you add surfactant, or water, or a non-polar solvent (like thinner or something) it will evaporate out.

I'm not a paint scientist or anything, but I think people are tending to talk past each other.

Acrylic paint is fundamentally: Pigment, solvent, binder + any other additives. Pigment is pigment, binder is an acrylic resin that causes adhesion and solvent is often water.

In this case I am using the word 'medium' to mean 'solvent'. Sorry :[

shmvo wrote:
Acrylic paint is fundamentally: Pigment, solvent, binder + any other additives. Pigment is pigment, binder is an acrylic resin that causes adhesion and solvent is often water.

In this case I am using the word 'medium' to mean 'solvent'. Sorry :[

Yeah, and right after posting I realized I was using "medium" to mean binder!

See what I'm saying, it all gets jumbled up...