Water Viscosity - How to change it.

[Kelly DeWinter]

Hi everyone. I'm an Artist and work with water colors and paint. I'm looking to change the viscosity (rate of flow) of water for my water colors.

I've tried working with:

. hot and cold water, (there is a minuscule change)

. adding starch ( works, but makes the art work flaky and does not adhere well to paper)

 

Is there anything that can be added to water, that will make it flow thick or thinner ?

 

Any suggestions would be appricaited

 

Kelly

[swansont]

Have you tried glycerine?

[Kelly DeWinter]

No I haven't, Can you give me an idea of what glycerin will do ? I'm hoping to find something that will keep the water clear . I'll give that a try/

[John Cuthber]

Glycerine will take forever to dry.

[StringJunky]

Wallpaper paste powder?

[Strange]

How about gelatin or agar-agar?

[StringJunky]

How about gelatin or agar-agar?

Gelatin was the one I was trying to think of.

[studiot]

Hello Kelly,

 

It would be useful to tell us more about the effects you wish to create.

Water itself will act as a paint thinner.

 

When you say water colour do you mean water colour or are you including what used to be called poster colour (powder paint you mix up with water) ?

 

What sort of quantity are you thinking of?

An addition of colourless alcohol or glycol would change the viscoscity of the water (which is already low) and have the advantage of evaporating along with the water. I assume you don't want to add sticky substances like gels to the mix.

 

The change is complicated and depends upon the concentration, but the viscosity will be higher than either individual liquid.

 

 

I remember an artist who created the most dramatic effects about 50 years ago by curdling indian ink with a small amount of water.

I will try to look out a photo of the effects, but this will take me a couple of weeks.

 

Another thing to consider is surface tension. This is likely to be more significant in thin films, such as used by artists.

The surface tension is reduced by adding a colourless detergent, such as used in chemical laboratories for cleaning glassware. This does not leave a residue on the glass so is ideal for your application.

Edited July 8, 2016 by studiot

[Strange]

The other variable is gravity.

 

How about writing to NASA and saying you want to be artist-in-residence on the International Space Station?

[swansont]

Glycerine will take forever to dry.

 

 

And yet people use it in watercolors. It does extend the drying time (which is one of the reasons it's used) but not indefinitely

 

http://www.naturalpigments.com/art-supply-education/glycerin-historical-watercolor

http://www.wetcanvas.com/forums/showthread.php?t=365927

No I haven't, Can you give me an idea of what glycerin will do ? I'm hoping to find something that will keep the water clear . I'll give that a try/

 

It's viscous, so should add viscosity, and as the above link indicates, it extends the drying time.

[DrP]

Other possibilities could include fumed silica fine powder, silica platelets or hydrocellulose thickeners?

 

Some thickeners give a thixotropic gel like effect so they wont drip or run, but will paint out easily under the brush.

[fiveworlds]

Xanthan gum is a water thickener. I used a particular brand of Xanthan gum while I was on internship in a hospital called nutilis clear.

[John Cuthber]

Glycerine will take forever to dry.

OK, for Swansont's benefit

Glycerine will take "forever" to dry.

[Strange]

OK, for Swansont's benefit

Glycerine will take "forever" to dry.

 

 

It is still used in watercolour paints, though.

[John Cuthber]

 

 

And yet people use it in watercolors. It does extend the drying time (which is one of the reasons it's used) but not indefinitely

 

http://www.naturalpigments.com/art-supply-education/glycerin-historical-watercolor

http://www.wetcanvas.com/forums/showthread.php?t=365927

 

It's viscous, so should add viscosity, and as the above link indicates, it extends the drying time.

OK, so I got round to checking the links.

The first one says "It was not until 1832 that William Winsor and Henry Newton, both painters and chemists, are credited with inventing 'moist' watercolors—pans of color moist enough for color to be lifted by the application of a wet brush. "

Well the point of adding the glycerine is so the stuff stays moist- indefinitely.

The OP says they tried changing the temperature but it didn't make a big enough difference.

I will have to guess here, but lets say they tried 30C and 0 C

That would give viscosities of about 0.8 and 1.8 (according to this)

http://www.kayelaby.npl.co.uk/general_physics/2_2/2_2_3.html

A range of about 2.2:1

 

well, if a 2.2 fold increase isn't big enough, lets suggest a 5 fold change

According to the other data there you would need a solution that has about 50% glycerine.

(We are no-longer talking about the painters who add the odd drop of glycerine to paints to slow the drying down.)

And the next question is what happens when you leave some 50% glycerine solution exposed to the air- how fast does it dry out?

Well, that's going to depend on the local humidity.

In fact if the humidity is high then it won't dry out at all.

the water from that atmosphere will condense out into the solution.

That's useful in another context. If you want to get air of a known humidity you can let it equilibrate with a known concentration of glycerine in water.

There's a graph of the concentration vs humidity in fig 1 here

http://horttech.ashspublications.org/content/2/1/52.full.pdf

And it shows that for a solution of about 50% glycerine, the solution will gain water if the air is above 80% relative humidity, and lose water if the humidity is below that.

So, what happens with real air?

Well the humidity is very variable but the average for indoor occupied places is fairly near 50%

Looking at that graph again, you can see that a solution of glycerine will be in equilibrium with the air if the concentration is about 80%.

 

Where does that leave us?

Well you can mix your pigments into a 50% glycerine: water mixture

Then leave it to dry, but the mixture will stop losing water then it reaches about 80% glycerine.

The remaining 20% or so of water never dries out (until the glycerine evaporates)

Say we start with 1 gram of the 50% mixture and we end up with an 80% solution.There's still 0.5 grams of glycerine there so there's 0.625 grams of the mixture.

About 2/3 of the liquid that was present initially is still there.

Do you consider that "dry"?

 

Eventually the glycerine will evaporate (actually it won't it will grow mould, but that's another story).

How long will that take.

Very roughly the rate of evaporation will be proportional to the vapour pressure.

The vapour pressure of water at room temperature is about 20 mmHg

And according to this

http://www.aciscience.org/docs/physical_properties_of_glycerine_and_its_solutions.pdf

the vapour pressure of glycerine is about 0.0001 mmHg

That's about 200,000 times lower.

One of the pages you cited says that the paint is drying in about 40 seconds.

If I have kept track of the zeroes correctly that means the glycerine will evaporate (to roughly the same extent) in about a hundred days.

of course the figure of 40 seconds is not for complete dryness, just too try to paint with.

Complete drying is probably something like a ten or a hundred times longer than that.

So, yes as Strange says- they still use it in paints.

And yes they do it for exactly the reason I gave- it stops it drying quickly.

If you used enough to increase the viscosity five fold- only twice as big a change as the OP ruled out as "a minuscule change" then you would increase the drying time to something like a month or a year.

Is that "forever"? perhaps not

https://en.wikipedia.org/wiki/Ars_longa,_vita_brevis

 

But, as I mentioned, what you would do there is really give the bacteria and fungi something to get their teeth into.

Ice cold vodka (about 6 times more viscous than water) might be better,

Edited July 9, 2016 by John Cuthber