Red Ochre – Under the Microscope


This is going to be one of my longer posts and graphic heavy.  All pictures are taken at 10 megapixels resolution.  If the picture is taken through a microscope lens it is a 20X microscope.

First some information and background on Red Ochre.

It turns out that red ochre has a lot of different names.  The easiest of which is really just a different spelling, “red ocher” but there are many synonyms for red ochre.  Synonyms are from “Il Libro dell’ Arte” by Cennino D’Andrea Cennini translated by Daniel V Thompson and “Medieval and Renaissance Treatises on the Art of Painting” by Mary p Merrifield.

– Brunes
– Bruno di Spagna
– Cinopis
– English Red
– Porphyry
– Rubea Terra
– Rubigo
– Sinoper
– Sinopia
– Sinopis
– Sinople
– Synople
– Spanish Red
– Terra ross d”Inghilterra
– Terra rossa di Spagna
– Terra Rubes

And those are just the western european names for it.  I’m willing to bet every culture has at least one name for this pigment.

So what exactly is red ochre?  “…(Red ochre is a form of hematite Fe2O3 used as a pigment)…” “Traces of the Past” Pg. 60

Red ochre has been used since pre-historic times and is the oldest pigment known to have been used by man..  “Within the last hundred thousand years both Neandertal (Neanderthal) and Cro-Magnon peoples used red ocher (hematite or Fe2O3) in burial or fertility rites, possibly as a symbolic replacement for blood” “Traces of the Past” Pg. 76.  It was used in the famous Lascaux cave paintings,  ancient Egyptians and obviously through the middle ages and renaissance and is still in use today.

Looking at pigments under a microscope can be both revealing and interesting.  So I took some samples and did just that.

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Three samples of red ochre dirt with a US dime for size comparison:  A large piece; a smaller piece; and “sand” particles.

All microscope pictures were taken at 20X magnification using a 10 megapixel camera resolution.  Sorry my microscope does not have a way to discern measurements under magnification.

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Large chunk of non-worked red ochre. Notice how the particles are clumped together.

Small chunk of Red Ochre.

Small chunk of red ochre.

“Sand” particles of non-worked red ochre.

The is what non-worked red ochre looks like.  Now we will take a look at milled red ochre.

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Fine mulled red ochre in a shell container.

Size comparison using a US dime.

Size comparison using a US dime.  It creates a small “cake” that conformed to the shell.  No additives were mixed in so technically this isn’t a cake but close enough.

Milled red ochre broken back down from

Milled red ochre broken back down from “cake”.

The particles of milled red ochre are much smaller.

The particles of milled red ochre are much smaller.

After breaking the “cake” up I milled it in a gum arabic water solution.  I took pictures of that under a microscope as well.

Red ochre in gum arabic suspension.

Red ochre in gum arabic suspension.

The edge of the red ochre in gum arabic in the shell.

The edge of the red ochre in gum arabic in the shell.

I also did one shell of red ochre in glaire.

Red ochre in glaire.

Red ochre in glaire.

Now that we’ve looked at red ochre under a microscope at various stages of being processed, what does it look like when being used on a support?

I made up four versions of the red ochre and put them all into shell containers.

1 – Rough red ochre

2 – Fine red ochre

3 – Fine red ochre in glaire

4 – Fine red ochre in gum arabic

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The four red ochres.

When doing a comparative analysis or testing it is important to make sure your samples do not contaminate each other.

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Each red ochre got its own water supply as well as brush. Brushes not shown.

I used two different supports, bristol vellum 100 lb (270 g/m2) and parchment.  I marked out four sections on each and painted them.  Each has a square in the middle for visual comparison.  Then I painted three “stripes” at the bottom edge to make viewing it under a microscope easier.

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Bristol vellum samples.

Of course the parchment strip I used wanted to curl.

Holding the parchment strip from curling.

Holding the parchment strip from curling.

Closer view of the parchment strip.

Closer view of the parchment strip.

As you can see the same red ochres on different supports looks different from one another.  The underlying support does make a difference in how the pigment is perceived.  Of course how the red ochre is made and what binder is used makes a difference as well.

That difference in how they are perceived by the human eye is a function of several intersecting areas.  Color and properties of the support, qualities of area coverage due to granule size, light quality and refraction off the granules, binder coloration and how the granules suspend in the binder, how the binder interacts with the support and more.  Did they know all these factors in the pre-1600 world?  Not like we do, but they did know what worked and what didn’t even if they didn’t always know why.

We know how red ochre look under the microscope from raw to put into the shell.  Let’s take a look at red ochre pigment painted on supports.  I used filtered water as the liquid to transfer the pigment from the shell to the brush to the support.

Roughly milled red ochre:

Rough milled was the least pleasant to work with on either support.  It took a long time to loosen up as a pigment for use. When it did, it was difficult to take up into the brush and wanted to rush down onto the support from the brush.  It felt gritty to paint with.  Coverage is a bit hit and miss with many times going over it with a brush or more pigment was needed.

Red ochre on bristol vellum.

Rough red ochre on bristol vellum no binder.

Rough red ochre on parchment no binder

Rough red ochre on parchment no binder

Rough red ochre on bristol vellum no binder thick coat

Rough red ochre on bristol vellum no binder thick coat

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Rough red ochre on parchment no binder thick coat

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Rough red ochre on bristol vellum no binder thincoat

No equivalent strip was put on the parchment.  I forgot to.

Finely milled red ochre:

Finely milled red ochre without a binder was the second least pleasant to paint with. That said, it loosened up nicely.  It was taken up by the brush with moderate effort and did not try to fly off the brush when the brush came in contact with the support.  It was not gritty feeling through the brush and covered nicely enough.

Fine red ochre on bristol vellum no binder.

Fine red ochre on bristol vellum no binder.

Fine red ochre on parchment no binder.

Fine red ochre on parchment no binder.

Fine red ochre on parchment no binder thick coat.

Fine red ochre on bristol vellum no binder thick coat.

Fine red ochre on parchment no binder thick coat.

Fine red ochre on parchment no binder thick coat.

Fine red ochre on bristol vellum no binder thin coat.

Fine red ochre on bristol vellum no binder thin coat.

No equivalent strip was put on parchment.  I forgot.

Using glaire:

Glaire was more pleasant to use on parchment than on bristol vellum.  It took significant time to loosen up with water and brush.  It went onto the brush in the amounts desired easily enough and went exactly where the brush told it to go.  It felt a touch resistant leaving the brush onto bristol vellum.  It was like a fine cream going onto the parchment.  Coverage was good and even more so on parchment but still so on bristol vellum.

Fine red ochre on bristol vellum using glaire

Fine red ochre on bristol vellum using glaire.

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Fine red ochre on parchment using glaire.

Fine red ochre on bristol vellum using glaire thick coat.

Fine red ochre on bristol vellum using glaire thick coat.

Fine red ochre on parchment using glaire thick coat

Fine red ochre on parchment using glaire thick coat

Fine red ochre on bristol vellum using glaire thin coat.

Fine red ochre on bristol vellum using glaire thin coat.

Fine red ochre on parchment using glaire thin coat.

Fine red ochre on parchment using glaire thin coat.

Gum arabic binder:

Gum arabice was more pleasant to use on bristol vellum than on parchment.  It took a reasonable amount of time to loosen up with water and brush.  It went onto the brush in the amounts desired easily enough and went exactly where the brush told it to go.  It felt a touch resistant leaving the brush onto parchment.  It was like smooth and easy going onto the bristol vellum.  Coverage was good and even more so on bristol vellum but still so on parchment.

Fine red ochre on bristol velum using gum arabic.

Fine red ochre on bristol velum using gum arabic.

Fine red ochre on parchment using gum arabic

Fine red ochre on parchment using gum arabic

Fine red ochre on bristol vellum using gum arabic thick coat.

Fine red ochre on bristol vellum using gum arabic thick coat.

Fine red ochre on parchment using gum arabic.

Fine red ochre on parchment using gum arabic.

Fine red ochre on bristol vellum using gum arabic thin coat.

Fine red ochre on bristol vellum using gum arabic thin coat.

Fine red ochre on parchment using gum arabic thin coat

Fine red ochre on parchment using gum arabic thin coat

The dregs left in the cups was also interesting to me:

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Rough red ochre water dregs.

Fine red ochre water dregs.

Fine red ochre water dregs.

Glaire red ochre water dregs.

Glaire red ochre water dregs.

Gum arabic red ochre water dregs.

Gum arabic red ochre water dregs.

I liked working with red ochre.  It is a straight forward pigment to make, much easier than my experience with brazilwood and certainly with making ultra-marine.  None-the-less it can provide its own challenges.  I enjoyed the process and tests I did.  I hope you learned something yourself and are willing to take the step into pigment making if you haven’t done so already.

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