Making Valazquez medium for solvent-free oil painting (marble dust, calcite, limestone medium )

Chalk and oil paint in the wild, gamblin oil colour, 1980 student grade line.

https://gamblincolors.com/oil-painting/color/1980-oil-colors/

...In order to reduce the cost of oil colors, some manufacturers use gels and waxes to stiffen colors and replace traditional pigments with less expensive ones.

Our approach is different. 1980 colors are formulated with pure pigments, the finest refined linseed oil and marble dust (calcium carbonate). More affordable colors have been made with these three ingredients since oil painting began...

Emphasis mine.

I've a couple of tubes for art class as these dry faster than my M Graham studio paints.  I noticed the texture was more enjoyable for the 1980 paints than winton which is kind of weird to work with as all the colours behave the same (oil paint shouldn't as each pigment is chemically different).

as part of the glazing experiments I mixed up some limestone calcite with regular linseed oil to make a stiff putty and added them to a few of the underpaintings.  It was about 10% putty to paint.

This sped up drying time a bit and helped the transparent colours behave less slippery when painting.  But still kept the transparent nature of the paint.  

As I was doing the glazing about a week later, I didn't notice any difference in the experiments with calcite added and the ones without.  I suspect if it was sitting a long time between layers, like a few months, that the difference would be more noticeable.  

I don't like using my stand oil calcit putty for underpainting.

Yes, mixing with the white makes it nicer to work with and a touch transparent.   But it dries slower and shiny compared to no additive, due to the high amount of stand oil.

I think it's time to make a tube of underpainting like one of the previous mixes I tried where the black and white chicken dried too fast.

About 2:40, she mixes in some chalk to modify texture and drying time.

My second batch that I tubed started to separate and oooze oil everywhere.

That could be because I didn't mull it much.

Conclusion I draw from this is that if I'm not mulling, make it fresh just before use

from here

Extender Medium, previously called Impasto Medium, is essentially colorless paint made with inert pigments in linseed oil. It is intended to be used as the name implies, to extend paint. It is made from marble dust (calcium carbonate) and barium sulfate which are typically used as modifiers for oil paint to improve feel and dry time. When used in larger amounts, these pigments are categorized as fillers, as in the case of student-grade oil paints.

Extender Medium is a translucent, pale grey paste that has a similar consistency to most of our oil paints. It has a very low tinting strength and only slightly lightens and changes the sheen of most colors when mixed in. An ideal use for the extender Medium is when you want to mix a larger quantity of straight paint and don’t mind a slightly less saturated color or a muted sheen. Using mixtures made with Extender Medium can be a very cost effective way to cover a lot of surface area. Underpaintings are a great opportunity to use the Extender. It can also help mix certain tints and colors that would otherwise not be available simply with the addition of white or other tube colors. A normal brushed out layer dries in about 3-4 days.

Looks promising.

And pretty affordable at the local art shop

This artist mixes their own calcite medium with rublev chalk and linseed oil of a ratio 2 powder to 1 oil.

https://workshops.kimberlybrooks.com/p/oilpainting

Online class specifically for the kind kind of painting I seek.  And at a cost above half my monthly income.  It's out of my reach, so I keep experimenting.  

It sure looks amazing though.

Marble dust painter spotted.  A new channel and one to watch to see where they go with this.

Hi R Ranson, hope your painting is full of fun and inspiring moments.
I have been reading some of this post and decided to reply before reading further lest I forget to reply.
Supposing one was to grind the limestone in a mortar and pestle if possible or a roller mill...,
and then that person was to take all that ground up rock and dust and wash it such as those who make their own clay by settling silt from the upper portion of the water...
And then let the water evaporate in the sun thus leaving the fine powder form as a "cake",
Do you suppose that fine powder or "cake" could then be milled or mortared again (once dry of course)?
Would that meet the level of fineness or microns you could use in your medium? Or might it be too fine?
I have not tried this yet. If you or others may attempt to do so, please share with us all both your successes and failures.
I for one would like to know if there might be anything learned from the process and if it has helped others,
Thank you for your posts. I will continue reading them now. Have fun and Good Luck!

That's a really neat idea.  We don't have limestone here (it's a bit of a geological island on our island).  So I couldn't try it, but I would love to hear how it goes.  You might be on to something.

Historically, it looks like they would use mostly wasts products from sculpture or other industries we don't have in abundance now.  

...

The other day, someone bought me high end gesso (the dollar store ran out of my normal stuff) and I was shocked by how gritty it is.  It's easily more gritty than the stuff I've been playing with.  This is usually caused by the same calcite used in the medium.  It's interesting to see what real gesso feels like.  But I don't know enough to say if it's related to my quest or not.

I honestly don't know yet and may have to try it myself.
Now where did I place those home depot style limestone rocks I pulled from the garden path or were they walmart style?
Or perhaps crushed shells or diatomacious earth such that the romans used to use for forming the mixture of concrete?

I suppose your 'Gesso' is as good as mine. lol I hope it works.

From The Artist's Handbook of Materand Techniques by Mayer.  First edition, 1940/41

Entries of note
Diatomaceous earth
Chalk
Marble dust (note, p269 is in the mortar section of mural painting)
Silica

From the same.  P90 and 91

Inert pigment

https://www.kamapigment.com/kama-products/pure-pigments/inert-pigments-fillers/calcium-carbonate-chalk-x-fine-3um-pw18.html

Best chalk dust for making the medium so far.  Although I bought it from a local store.  

Also known as Meudon white, marble powder, or Spanish white, this product is precipitated chalk powder. This grade (the most popular) is primarily used in the manufacture of gesso and other coatings for painting.

Chemical Formula: CaCO3.
Colour Index: Pw 18
Average Particle Size: 3 µm (microns)

It's very smooth when blended with oil and dramatically increases transparency of a paint when mixed 20% medium to paint.

I keep seeing references to Constables paint box having a lump of gypsum in it when he died (cause of death not related).  There seem to be a lot of theories as to what he ussd it for.  But also, a lot of variation at to if it was limestone, gypsum, or chalk.  

Constable mixed a lot of his own paints on location, so I can't help but wonder if this was related to adjusting the texture or qualities of the paint or if it was just a nice rock he found on the ground and he kept it because it's lucky or something.

Observation

If more than 20% calcite medium to paint, there is a noticeable value shift or sinking in, as the paint dries.

However, there are times this is useful, like increasing the transparency in the shadow area.

This value shift is more noticeable with darker colours and earth pigments like umber which have a strong chance of sinking in anyway.  

It returns to the proper colour with oiling out. Varnish should do the same, but it is possible we need to apply oil and let it dry before vanishing.   A good experiment would be gloss vs matt varnish.



In the picture, beside the red jug the wall colour is oiled out and returned to normal whereas the rest of the wall colour has lightened as it dried.

Another thought, we could use stand or bodied oil in the calcite mix to limit the sinking in.  But as this is lower layers of paint, I didn't want to risk too much gloss, making the surface harder to add future layers of paint.

I also want to keep the drying time consistent and predictable so I wouldn't break the flexible over less flexible rule (fat over thin, slow drying over fast).  Future layers have less calcite and more oil.  


Thinking more, the solution is not to exceed 20% calcite medium to paint unless there is a very specific reason.

https://justpaint.org/on-the-yellowing-of-oils/

The next two variations, which include the addition of barium sulfate or precipitated calcium carbonate, become increasingly less yellow while also showing a corresponding drop in oil exuding to the surface or out the sides.  

Although this study is still young and inconclusive, it suggests that extender pigments like calcite might decrease the way paint yellows as it decrease the amount of excess oil that rises to the surface as it cures.  Aka, calcite helps bind the oil better than pigment alone.  Possibly.

The study needs about 100 years more to be conclusive.

But it would be interesting to do a home experiment of titanium white and yellowing, including 1980 (calcite filler) and calcite medium as well as control groups from the tube.

Mixing calcite medium for impasto and improving transparency.

Gives a good view of the texture.   Although, seems a bit soft for impasto in my expierence, I also know that calcite varies in how it behaves, so it might be just right for him.

I'm feeling very much like I nailed this calcite thing.  Or at least understand the basics.
Here is a summary of where I am at, at this time.  I'm sure there is more to learn so I'll post observations as they occur.   It's a comfortable, safe, and affordable medium and most importantly, customizable to the situation.   I'm using it in most painings these days.



It helps to think of it like a paint with a moderately fast drying time (about the same as most earth pigments, but not as fast as raw umber or lead), high transparency, and matt or gloss depending on how we mix it.  Basically it's paint with PW18 pigment (Chinese white) which is transparent in oil.  

The Valazquez medium sold by rublev is fairly high gloss, or so I've heard from painters who used it.  But that uses mostly stand oil, so it's good for upper layers of painting and glazing.  It's easy to mix the calcite with linseed oil or even use coarser calcite for even better adhesion of the next layer.  

Underpainting and first layers.

Mix stiff paste of linseed and calcite.  Mix into paint up to 50%.  Use with fast drying and moderately fast drying pigments.  Improves drying speed by about 20%.  Increases transparency so keep that in mind when choosing an underpainting colours.  

I like this on a yellow ochre midtone gesso, raw umber and white to block in the big lights and shadows.



Options:
- alkyd
A few experiments adding M Grahm Alkyd walnut medium to mix the calcite paste have given me the conclusion that there is a lot of potential there, but not so much for me.  Too much alkyd makes the paint glossy and resists the next layer of paint.  Too little and it doesn't do any benefit to the drying time but is more expensive than linseed oil.   It would take a while to find the Goldilocks spot.  But I don't like the sticky texture that Alkyd medium adds to paint.  Like extra drag... I don't know how to explain it.  Alkyd medium makes paint feel sticky to me and I don't likes it.

- coarser calcite
Using coarser ground calcite makes a very slight texture to the paint that makes it easier for the next layer to grip to it.  A lot like good quality gesso has a bit of "tooth" to it.   Too coarse and it feels like painting with sand.

The coarse or fine grinds also appear to influence drying time.  Coarser appears faster.  This needs some experiments to be certain but it makes sense logically.

Regular painting

This medium is lovely for changing the flow of the paint.  I can mix up a stiff mixture for greasy paint, and thinner mixture for stiff paint.

For this, I find no more than 20% of the medium to paint is best.  Less is better.  

These layers do best with the finer calcite, usually sold as PW18 so it has a similar texture to the tubed paint.  

Although it won't make an opaque paint transparent (just choose a different pigment) it does add a tiny bit of transparency to opaque paints so the under layer will either add glow (if white underneath) or add depth (if raw umber or whatever your dark in your underpainting underneath is).  

Where it shines is increasing transparency to already transparent colours like ultramarine.  

The picture above, the woman has a blue skirt.  So I put the first pass with just ultramarine and calcite medium to almost glaze.  The next layer has some white to bring back the highlights, but mostly just the ultramarine calcite mix for the rest of the skirt.  Unfortunately the glow doesn't show up on camera.  But if I was to paint this normally, I would have to mix colours in with the ultramarine to darken it.  Instead, the underpainting dark is doing the work for me.


(not finished or varnished yet - so there is some sinking in and the glow won't show on camera anyway, the wall and face both get improved after this)

It's like a gemstone where the light enters the paint layers and reflects back.  If the setting of the ring is shiny or white, the gem glows.  If it's dark or tarnished beneath the stone, the gem looks dull and can even seem to draw light into it.   I'm very happy with these results as it looks like my memory of the national gallery in London (although this painting isn't there, they do have some from that time).  

For this painting, there is a lot of scientific studies with pigment analysis and the like.  I tried to be as true to the original as I could with the budget and resources I had.  If I had to substitute pigments, I tried to match not just the colour (hue) but also the other pigment properties like transparency, dry time, etc.

Regarding calcite, the analysis of the original and the papers I read all mention calcite in the different layers - especially the under painting.  All of them dismissed this as contamination, disreputable pigment sellers, or were simply confused why Vermeer would bother with calcite in these layers.  It's a low-cost filler that modern paint makers use - so calcite is viewed with distain in our modern eye.   This is one of the reasons I choose this painting - because we have an approximate ratio of calcite to other pigments.  I followed this as closely as I could while compensating for modern pigments.  

I feel strongly it worked.  

But it also required thinking of the painting more like watercolours than like modern painting.  Thinking about how light will penetrate or not depending on the mix.  Not just thinking about the colour: hue, saturation and value like modern colour theory, but thinking of paint like it's a real, physical thing that interacts with light.  I think this is what's missing in a lot of modern paintings.  

Um, main paint layer options
- changing the kind of oil changes the dry time and gloss.  For top layers and glazes, I like to use a mix of about 2:1 (two parts walnut oil to 1 part stand oil) to make the putty as this has a nice glaze.  But it's a pain if I have to paint over it.  When in doubt, use artist grade linseed oil.

- this won't teach a dog to lay eggs.  
This medium shines when combined with the understanding of how the individual pigments work.  Dry time, transparency, etc, might change slightly, but not significantly.  Choose the pigment correct for the situation, then add the medium to it.  

Likewise, we still need to consider the golden rule of "more flexible over less flexible" when it comes to oil paint.  This medium isn't fat or lean.  It's basically a transparent, moderately fast drying paint.  It's behaviour in drying and cracking is about like yellow ochre.  If using it in later layers, I use less calcite medium or I change to walnut oil if it's going on top of a slow drying layer.  

Future areas i want to explore include calcite as impasto medium and I've had some luck using it to improve the behaviour of cheaper oil paints

Wow, R, you’re getting some nice paintings!

I’m not a painter, and I don’t know if this is common knowledge.  I had an assembled ashford spinning wheel to finish, and I followed up on a mention of shellac.  It’s a resin excreted by an insect.  You can buy it in flake form, just dried bug stuff.  You dilute it with ETOH.  It comes in different colors.

It dries quickly.  When you put another coat on, prior applications can be re dissolved.  It’s transparent and dries glossy.

When you were describing the attributes of your new medium, it was a lot of the same language as shellac.  Not the same qualities, but interest in the same things.

Just in case it’s useful information…

Very neat.  I'm learning more about shellac this week in furniture and oil paint.  When it Oand distilled alcohol) became available in europe, it was used with some colours to increase glow.  But the details aren't clear how.  

I also am about to experiment with some old chairs as we can clean it by melting the shellac with alcohol and rubbing it around again.  This should help me learn more about it's behaviour.

Does it darken with age?

I don’t know about darkening with age.

Did you buy premixed commercial shellac?  To extend shelf life, they may have added some weird or toxic gick.

If your old chairs are shellacked you could get the old shellac off with just high proof ETOH.  Do your old chairs appear to have darkened?

Were you able to find shellac in your region?  I had to order on line.  Best place I found was “shellac shack”.  (He is located in Oregon so the shipping is pretty quick for wet coast and for Colorado). The man there was very helpful on the phone and has lots of information on the website.

He would probably be quite generous with his experience.

Shellac is used in foods and medicines.  Doesn’t seem like a dangerous substance.  The alcohol you dissolve it is is probably more risky!

With furniture, there is usually a need to remove the old shellac as there should still be lots on there.  I've been told to wipe the alcohol all over and it redistributes the old shellac which is, I'm told, usually better quality than anything we buy these days.

The flakes are easy to buy here, but not artist grade, those i probably need to order from an art store.

Love this. I made a note to read it later as I'm checking emails with morning coffee on the porch before I get in the greenhouse!
This makes me think of the time my friend Madeline and I did a Crape Myrtle draw down! We were definitely amazed at the result!

Can't wait to have more time on the homestead for art. Ive been thinking about my future pottery barn and sculpting studio waaaaaay to much this spring!

Hope y'all are well.
Dustin

Here's another example of how I'm using the calcite medium.



I really like this style of starting a painting with a value study.  Although, the method adapts with each painting.  It uses very little paint and often only one colour at a time for the early layers.

The gesso is tinted with yellow ochre or something to make a light midtone.  I apply raw umber with a stiff brush to the darkest darks.  Use as little as possible and scrub it into the canvas.  

Then i mix some marble dust and linseed oil to make the same consistency as the paint.  Mix these together about half and half.  Use these for the less dark dark areas.

Let dry, add white if wanted for the next layer of the underpainting.

When that's dry, begins colour.

https://www.wetcanvas.com/forums/topic/safe-solvent-alternatives-eco-solve-paint-thinner/

The question is about how to get that thin wash underpainting that became popular with the rise of solvents in the mid 20th century, but without solvents.

There are alternatives to solvent that still allow you to apply thin layers at the begining of a painting, the two I use are marble dust and lavender spike oil. To use marble dust I mix 4 parts paint with 1 part marble dust and add half as much linseed oil as marble dust. This creates a paint that you can spread thinly and makes the paint more transparent and it will dry in a day or two. Lavender spike oil, though it is a solvent, will not cause any of the health concerns associated with mineral spirits. The one big downside is that it takes longer to dry than traditional solvents, but it does make oil paint leaner as well as physically thinner. If you just want to make your paint dry faster without thinning it much than you can add a TINY amount  of a whole beaten egg to your paint. Be careful, a little goes along way. I hope this information will help you in your solvent free journey. I would also recommend you get the book “the new oil painting” by Kimberly Brooks.

Happy painting!

Bold mine

Beautiful video on a valezquez master study




Note the mixing of calcite putty medium at about 35 seconds in.

Wet canvas discussion turns to calcite

https://www.wetcanvas.com/forums/topic/limited-oil-mediums-painting-without-mineral-spirit-and-anything-like-that/

A few months ago I tried to mull a calcite medium to make my colors a little more transparent and to stretch them.
Unfortunately, it turned out to be a bit gritty, even though the calcite is said to be very fine according to kremer’s data sheet.
I thought that it were hardly noticeable mixed with oil paint,
but I need a certain amount of it to stretch the paint noticeably.
Unfortunately, the oil paint mixed with it turn gritty as well.

My instinct is that this is calcite for gesso and not fine enough for paint like pw18

Looks like the next poster felt the same way

Kremer says their Calcite’s “average particle size is about 20 µ”.  That’s too coarse for a medium.  Hand grinding it won’t get you anywhere.

You’d be better off buying this: “Purified Calcium Carbonate has a very fine and controlled particle size, on the order of 3 micrometres in diameter” https://arttreehouse.com/artstore/product/purified-calcium-carbonate/

Or this – 3.5 microns size for the extra fine:     https://www.naturalpigments.com/chalk-calcite.html

Or buy extra-fine calcium carbonate already ground into a paste:  https://www.naturalpigments.com/velazquez-medium.html#details-about-Velazquez-Medium

Good list, even if old. To that I would strongly recommend Kama extra fine.  (Kama from canada linked above...never tried this kremer source but a lot of mad scientist painter types on wetcanvas talk about it as a source for supplies)

Note, microns are brain twisters.  Smaller number is finer powder.

The next post says 20 microns which is about the same as fine human hair or moderate marino wool.  

Well, it should be more of a transparent oil paint than a medium. I said medium yesterday because I don’t use it pure, like oil paint and for this, the grain is finer than some pigments used for oil paint.
I bought the calcite years ago, and I couldn’t find any ground calcite anywhere else. :unsure:

Great, import costs and very high shipping costs, if they even deliver to Germany.
I can order from Kreativ.de, boesner, some Dutch shops, Jacksons Art and a few others. the problem is the shipping costs for one thing.

20 microns is very fine. do I now need one that is nanometre fine? Can I somehow get it finer by using a mortar?
4€, a few euros for the linseed oil and one afternoon work spent for nothing. :(

Otherwise, I have some champagne chalk, kaolin, lithopone, zinc sulphide, barium sulfate, pyrogenic silicon dioxide. Is any of that useful for a transparent oil paint?

If memory serves, one of the tests above turned out like that.  I'm curious to go back to that calcite and use it in underlayers as it removes the problem i have where later layers of oil paint bead up.

We get the discussion on how hard it is to make the calcite finer at home, then

Here is calcium carbonate, natural, approx. 1 µ, very white, from Kremer Germany. https://www.kremer-pigmente.com/en/fillers-und-building-materials/colorless-und-colored-mineral-fillers/carbonated-chalk-marble-and-others/1878/calcium-carbonate

Of the things you have – the champagne chalk could be used, but it may be darker.  

Champagne chalk is new to me.  I'm off to find out what that's for.

Some interesting conversations in the archives of wetcanvas.  Not linking here as it's a reoccurring theme and not very practical.

The belief is that since calcite, marble, limestone, etc, are all opaque powders, they make an opaque medium.

However, these beliefs are also forcefully promoted by people who have never worked with calcite in oil.  

The artist handbook refernced upthread has some good science on how the particals, when suspended in oil, are, for practical purposes, transparent.  Myers deep dives into the science of light,  particle shape, refraction, and other whys, even if he only gives it a few paragraphs.

Often the conversation wonders into the translucent vs transparent.  Some seem to think it only makes opaque pigments more transparent.   But the tests they use to prove their point are poorly done.  And not done by the people shouting the opinions.

That's been one of most difficult elements of learning about this medium.  People seem to take a strong stance one way or another and don't always look with their eyes at what's happening.

My expierence so far,
. Particle size makes such a difference, most of the conversations are basically talking about two different things. (Calcite for gesso, vs calcite for paint medium)
. At 20% volume calcite putty to paint, it doesn't do much to improve transparency in opaque colours, but it can make a lovely glow in transparent colours.
. Needs about one to one medium to paint to start changing transparency in a semi-opaque colour like raw umber...which isn't in alignment with "best practices". Far too much medium.
. Even at a 4 to 1 (medium to paint...aka, way too much medium), there is no wrinkling of medium.  But I don't paint in impasto style and keep my layers fairly sparce.
. I don't think calcite is the answer to making thick, transparent sculpture out of oil paint.  Although it might help when combined with other extender pigments i have read about.  I suspect encaustic (wax heavy) painting would be a better direction to look at.

Haven't posted in a minute, but have you experimented with linseed oil, or would that spread to much into the rest of that work? Haven't tried it myself yet, just came to mind. Forgive me I read farther back and see you did. Another alternative  might be coconut oil, but in my experiments with making makeup it removes makeup rather quickly so coconut might not be great, or it may. Haven't seen it used with pigments yet.would test it on a scrap canvas with various pigments and mediums first and see what the effect is first perhaps.
Be blessed,
Larry Jackson

I use linsed oil all the time. If the paint needs it.

Linseed oil makes paint more runny, slower drying, and increases gloss.  It's awesome stuff and for stiffer paints like winton or old holland, I use about 1 drop per large fava bean worth of paint.  Maybe upto 3 drops per fava for some pigments.

It's often easier to oil out (couch) with linseed oil where we rub the oil into the surface of the painting before painting.

The biggest drawback of linsed oil is that modern artist refined linseed oil can yellow quickly if there is not enough pigment in it to make chemistry happen.  Too much also makes a soupy mess that is difficult to control with a brush.  Too much linseed can also alter how the paint film dries and cause wrinkles or cracking.   So it's good to use as little as needed to solve the specific problem.

The calcite putty is basically transparent(ish) paint.  This solves almost all the problems that linseed alone can cause when used in excess.  I appreciate how I can adjust the recipe to loosen or stiffen paints.  I can also change the oil to make paint longer (sort of stringy, thixotropic, like melted motzza) or short (doesn't make a string) or self leveling or leaving brushmarks... a lot of these things would normally require a vast collection of fancy mediums, not all as safe as I need.

Linseed oil and calcite putty are both very useful tools.  However, outside of experiments like i share in this thread, I find I adapt the position:  Only add stuff to the paint to solve a specific problem, and then add as little as possible.

There are definitely times when I want the effect the putty gives.  Or the linseed oil.  Or, like today's painting session, both. I'm starting the final layer, which is details over a simplified colour layer.  I want the shadows to glow more, so the darker colours have about 10% calcite putty made with stand (self leveling brush strokes).  I've also oiled out the surface before painting with a tiny layer of oil so that I dont have to repaint the whole area,  the brush strokes can smooth on the edges and optically blend with the colours from earlier layers.

Most of this painting was painted with paint from the tube, no medium or oil added.  Except for the very first layer which had some calcite to make the raw umber behave how i wanted, and this final layer that is just beginning.




The background (floor) of the bottom left is just starting and hopefully you can see the details like rocks and ground texture don't require a complete repaint of the whole thing.  Thus oiling out.

Shadow glow doesn't show on camera.  Although this might help give an idea.

The picture on the right is a highly colourful (too much for the image) printed version of the painting.  The printer went colour mad.

Because of the limits of our screen and camera,  it looks pale next to my painting of the milkmaid.  That gap in colour and saturation between painting and print is almost as big as the gap between screen and reality.   The glow the calcite made in the darks really makes the lights sing.



We can also see this when viewing old master painting in person vs what we see on screen, especially the Dutch masters, who we now learned used calcite in some of their layers.  The glow is amazing and I've never expierenced anything else like it.  Maybe one day I can be that good.  Just got to keep painting.

The more I learn about painting, the more it feels like an exercise in problem solving.  Paint alone can do a lot.  But sometimes we need a little bit more to find the solution we are chasing.   Each ingredient solves a different problem (and usually causes new ones).

Anyway, there are a lot more details about my every day painting in the private group.  I realized  now that i share so little painting publicly that it's probably easy to think I've gone calcite-mad.

Another wetcanvas discussion on using chalk to make a medium

https://www.wetcanvas.com/forums/topic/painting-with-stand-oil-and-chalk/

And yet again, another person trying to make a transparent impasto medium, to make it easier for painting thickly.

There is some interesting stuff about yellowing issues in a moment, but first, the start of the thread.

I am thinking about using Stand oil [polymerized linseed oil to {what consistency?}] with chalk to create more texture in my paintings of trees, because “Coatings prepared from stand oils are less prone to yellowing than are coatings derived from the parent oils”. I already make my own paints, so I know enough about it to start thinking about this.

But how much less?

And how much chalk powder should I use in the stand oil? Only enough to keep it from dripping down the canvas? But not so much that it will be difficult to paint with….I think I need a formula to start with.

So what I need to know is “will it thinken up AFTER adding the chalk?”

From my expierence, stand oil is a poor choice for this as the self leveling properties increase when mixed with chalk.  

It's not clear if the goal is to use this as a coating on top of oils, in which case, wax based product might be better.  

But if used as a medium to mix with paint, I would look at the ingredients in rublev impasto medium.  I got to work with it in class and it's pretty good stuff.  It has a high amount of chalk and linseed (not stand) oil.  It has a few other ingredients to make the paint quite stiff.   Chalk and oil putty tends to smooth out when it mixes with paint and I have to make quite a stiff paste to get impasto effect.  Start at 1 to 1 oil to calcite, expect to work (and i mean work) up to 2 to 1 or more powder to oil.

Gigalot
Spurgeon highly recommended his putty but I found it strongly yellowing and even brown. At least one of my painting darkened due to calcium carbonate overload.  

I wonder how much putty is used and how thickly the paint is applied.  I haven't seen this symptom yet, but I paint very sparce layers and usually keep to less than 20% medium to paint, usually 10%....except for my first layers, but this is only mixing with umber so I couldn't tell if it darkened.

Here we go

Chalk and oil probably yellow so well because it’s transparent with no colour and the thicker oil paint films will display the thicker yellowed oil layer.

This makes sense as pigment (somehow) reduces the yellowing or apparent yellowing of linseed.   Calcite behaves like paint, but without the advantage of pigments.

Like any medium, it's important to use only as much as needed to solve a specific problem, and no more.

Yes, paint loaded with a lot of calcium carbonate filler and especially with fumed silica became more transparent. Extra amount of oil content will increase yellowing and even browning. At least my own painting darkened because I decided to try to use calcite/linseed oil paste on it after Spurgeon’s advertising of his “chalk putty” method.

I need to learn more about this Tad guy.  I ran across him when trying to figure out why the universal truth that linseed oil yellows doesn't apply to very old oil paintings.


In other news, wetcanvas is a failing site and isn't entirely archived on the waybackmachine yet...if ever as the server is down for about 6 hours out of 24.  So I'll probably be doing more of these reaction posts so all the information I find is gathered in one place.

However, my expierence changes with time, so will my opinions.  I don't think I've even scratched the surface yet of what this medium can achieve.   That makes me very happy.

More wet canvas
https://www.wetcanvas.com/forums/topic/is-it-wise-to-mix-calcium-carbonate-along-with-galkyd-gel-into-paint/

Original question was about mixing a calcite rich medium with a alkyd medium to improve dry time.

Back to your question – Calcium Carbonate added in ends up making a more self leveling putty than a gel for me no matter what I mix it with. ...

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There might be an issue adding only more solids (the calcium carbonate) to your paint since the paint is already going to be at the max binder to pigment ratio, so I would be adding the filler to some other liquid such as linseed oil or the medium rather than to just the paint.

I do find my calcite is more likely to self level... but this impasto stuff would be a good area to explore.  I have used it to stiffen paul rubens student grade paint wich is a bit more runny than even m Graham.