Max reduction of acrylics with water

Ran across this on internet. Basic statement is if one reduces acrylic over 30% the paint may flake of non-absorbent surfaces. Maybe not if it's clearcoated. Interesting thought, anyway. Link :

Interesting vid but don't agree with her understanding on some aspects, especially as she doesn't discuss mechanical bonding, rather she assumes its chemical. Bonding between paint molecules is generally chemical using a binding agent or binder as we call it. That doesn't magically float away, it remains and creates a bonded matrix of pigment and bonding molecules, its the suspension fluid that does be it oil, water, alcohol etc. Though in most cases the bonding to the substrate itself is done mechanically..Either by trapping it within the fibres say of canvas or paper or by the hills, valleys and roughness we create when prep sanding and thus later pigment molecules can then bond to those mechanically bonded to the surface..It is really important when video makers and those educating through such means that state 90% of painters out there don't know this "next fact"..that they actually get it right themselves LOL. Our issue in Airbrush is binder breakdown when over-reducing but thats generally something that happens within the paint itself as it creates a paint that appears grainy or has a separated look, it will still push out molecules of pigment but they will simply be further seperated and may result if them not binding well to other paint as it can't form that strong matrix but that pigment molecule will still bond to a substrate through mechanical adhesion. This is because most binders are organic and some "thinning" agents will break that molecule down and render it useless, (airbrush though often uses synthetic binders which are more resiliant), thus reducing chemical adhesion. There are also possible hydrolytic effects of the trapped carrier or suspension fluid pushing the paint off, cracking it etc, most oil painters are well aware of this effect of trapping solvents and why it must "cure" correctly before putting more on....But she does at least sound like she knows what she's saying LOL..But do agree that adding more binder when reducing is a good idea, especially if using water as a reducing agent as it has no binder added..I use Jo Sonja's Airbrush medium for exactly that purpose when home making paint from dyes and the like. To add, understanding the "charge" of the molecule is also important. Some molecules may both have negative charge and in that case naturally want to repel..papermakers have this issue at times when using dyes and paints to color pulp.

You will see she has disabled comments because everybody was giving he flack for that statement. But I do agree. But I'm no expert. If I want transparency, I use medium. When I need flow, I use water. But the correct pant also helps. If you like painting detail and smooth transitions, do not buy a heavybody paint.

with etac paints Bill recommends to not over reduce the paint with water . 25% water to your paint should be the max .
having said that I used to reduce it way more than that up to 1 part paint to 20 parts water without a problem but that was only for a white wash and I dont do that anymore now I cant see what I am doing with that over reduced paint
Like Andre I use the transparent base to gain more transparency and hardly ever use any water