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Mosaic opus: an old subject with a new twist.

Mosaic opus: an old subject with a new twist.

Mosaic opus definition: the different ways of laying the background in a mosaic. Plural: Opuses or Opera.

Leaves and fruit. Photo and mosaic: @Helen Miles Mosaics

Mosaic Opus – Time for an Update

Infilling detail. Photo and mosaic: @Helen Miles Mosaics

You might be forgiven for thinking that I am a bit of a traditionalist. ‘Contemporary mosaics inspired by ancient designs’ has a distinctly tweed coat and brogues ring to it. And then there all my blog posts about ancient mosaics and fewer about their contemporary equivalents so really I wouldn’t blame you for being convinced that I wear knitted cardigans and have a deep fondness for Anita Brookner novels. But buried within this buttoned-up exterior lurks the heart of a rebel and when it comes to the subject of opuses in mosaics that rebel is chafing to get out.

Cockerel. Photo and mosaic: @Helen Miles Mosaics


My opus rebellion is one of those quiet ones that disgruntled children excel at. Not saying anything, perhaps. No screaming and slamming doors, maybe. But a pervasive presence and a body language that’s as clear as a siren that says whatever you have decreed is not well received and will just not do. You might not be able to see me but my arms are crossed across my chest, my shoulders are hunched and my bottom lip is protuding all because I feel that the opus-sayers, the shadowy figures who decide what is an opus and what is not, have apparently checked out and forgotten to turn off the lights.

Lemon tree detail. Photo and mosaic: @Helen Miles Mosaics

The opus, or way you lay the background in your mosaic, is fiendishly important. When you are designing a mosaic you need to consider how you will approach the opus alongside other elements in your work. It can’t be left as an after thought. It might not count alongside American politics  and the great European debate as a topic for dinner table conversation, but it is the opus which is the bones, meat and soul of a mosaic. Never mind the design – a design is a design – but pay attention to what is going on in the background of a mosaic and it is there that you will find the melody, the choreography, the spirit of a mosaic. Different opuses achieve different effects.

The Traditional Types of Mosaic Opus

If you are looking at ancient mosaics (which I do a lot) this is the classic one, the old faithful, pinstriped suit and briefcase one. It’s called opus tessalatum  and is where the artist lays the background tiles in straight rows as in the example below. The effect is calming. It’s not going to call attention to itself so the eye remains focused on the central feature of the mosaic.

mouse and walnut mosaic_completed
This is a copy of a detail from the famous ‘Unswept Floor’ mosaic in the Vatican Museums. @Helen Miles Mosaics

Opus Regulatum is where the tesserae are laid in a grid like the sheets of mosaic tiles that can be bought pre-made. Again, the effect is to keep the eye focused on the main design but that design feels as if it is floating or pasted on the background as opposed to being embedded in it. Here you can see Opus Regulatum being used in the background of London’s famous underground mosaic designed by Eduardo Paolozzi:

Paolozzi mosaics_Central Line platform.
Paolozzi mosaics_ Central Line platform. @Helen Miles Mosaics

Opus Vermiculatum is among the oldest of the opuses with the earliest examples dating to 200BC. The name refers to the ‘worm-like’ quality of the work, and refers to a fine, detailed laying technique using very small tesserae which are closely set with the aim of producing painterly effects with gradations of colour. The technique was especially used in ancient emblemata – the central motif of early floor designs.

Opus Vermiculatum.
Andamento: Opus Vermiculatum. Emblema panel, Palazzo Massimo Museum, Rome. @Helen Miles Mosaics

Opus Musivum is a joyful, foot tapping kind of opus which entails laying the lines of the background so that they radiate out from the design like ripples in a pond. This opus brings more movement and liveliness to the mosaic than the ones above.

Opus musivum. Photo and mosaic: @Helen Miles Mosaics

Another alternative is opus palladianum which is a fancy name for crazy paving or laying your tesserae of all different shapes and sizes in pretty much any way you like. It is a deceptively difficult opus to do well on a small scale as although there is no need to fuss too much about cutting, you need to keep the spaces between the tesserae regular and to ensure that the tesserae maintain a relationship with each other. However, it’s a useful opus for large background spaces and is popular for community projects.

Opus Palladianum. Photo and mosaic: @Marian Shapiro Mosaics

Then there’s also opus circumactum, a series of little fan-shaped flourishes which are wonderfully elegant, opus sectile which entails cutting the tesserae into precise shapes to fit together like a jigsaw and the rather obscure opus spicatum which is a herring bone pattern like this Byzantine-era brick work.

And finally, the delicately airy opus signinum where fragments of tiles, earthernware, pebbles or tesserae are set into a mortar bed:

Opus Signinum. Photo:

But, dear Reader, if you have been paying attention you will have noticed something a little suspicious about the opuses. They all have Latin names. What does that suggest to you? It suggests leather chairs, flock wallpaper and plumes of cigar smoke, that’s what. It does not suggest that the shadowy opus-sayers have looked up from their newspapers for at least one hundred years. So let’s do their job for them.

The New School of Opuses

Opus opusum

Definition: the opus is the mosaic.

It’s a way of doing things that lets you escape from the rules and ‘ums’ and start all over again. It’s a game changer like the Renaissance or Darwinianism or the Theory of Relativity. It’s liberating, exciting, innovative and fresh. It’s putting a guetto blaster in that fusty opus-sayer reading room and turning up the volume. There are too many brilliant examples to list them here but the name that always comes to mind for me is Julie Sperling who uses opus opusum to make deeply beautiful and politically powerful mosaics about climate change.

Opus opusm. Dialogue. Photo and mosaic: @Julie Sperling Mosaics

Opus Drostleum

Definition: A mixture of squares and rectangles laid with all the panache of opus palladianum but with restricted shapes.  Named after Gary Drostle who uses it to stunning effect in his California Seashore Trail Mosaic Project.

Drostle opus.
Opus drostleum. Photo and mosaic: @ Gary Drostle Mosaics

Opus Fluctum. 

Definition: A way of laying undulating rows of tesserae as if they were mimicing waves but not limited to sea themes. The rows weave into each other using triangular tesserae. Gives a whimsical, light feel like summer breezes.

This is the one I go for. Opus Fluctum evolved as the result of experimentation and now I often use it as a matter of course. I found that I used to dread the background stage of laying mosaics and so I began playing with the andamento and Opus Fluctum keeps me totally immersed and fully engaged.

Opus fluctum, detail, one. Photo and mosaic: @Helen Miles Mosaics

Opus Strictum

Definition: Widely used in Greek schools of mosaic. The tesserae are laid very close together (the closer the better) the mosaic is often made in reverse before casting and the andamento is not given prominence. Similar to Opus Vermiculatum but without the finesse. . 

Opus strictum. Athens Mosaic School. Photo: @Helen Miles Mosaics

Opus Variatum or Biggsum

Definition: use of varied and contrasting background laying patterns in the same piece. A useful technique to visually divide a single work into distinct sections. Named after Emma Biggs who uses it to stunning effect in a number of her works including this one: 

emma biggs opus variatum
Opus variatum or biggsum. Photo and mosaic: @ Emma Biggs Mosaics



  1. A really fun article, Helen! I’m partial to opus fluctum myself 🙂 There is definitely whimsy to it, which I love, as well as an openness, vulnerability and lightness. Our choices in andamento are a nice reflection of who we are.

    1. Thanks, Christine, and I think you’re quite right. I want to write about expressiveness in mosaics in another post as I think many people feel that mosaics aren’t an expressive art so I need to prove them wrong!

  2. Jyoti

    I’m both thrilled and depressed with this post 😉
    Thrilled because it covers newer opuses than those covered in the books in my library, and depressed that with so many varied tile laying styles, my decision to decide on one gets tougher than ever 🙂
    Some day I’d discover how you found Opus Fluctum to be your thing! You do create beautiful effects with it.

    1. Some day indeed! This blog post was originally going to be dedicated to you because I started writing it in order to answer your question about my use of andamento but it kind of expanded into something else so I am afraid the original post will have to wait until another time but I promise you it will come. 🙂 Meanwhile, I hope that having all the options described makes it easier to choose an opus – it does seem rather odd that the old opuses had never been updated.

      1. Jyoti

        Thank you for the thought 🙂
        I look forward to the next post, whatever aspect of mosaics you feel inspired to cover. I don’t know if I’d imbibe your precision and fun waves but they sure fascinate me a lot!

  3. Jyoti

    Also, Opus Signinum in the image above reminds me of (Indian) Gujarati tie and dye style colouring of cloth called Bandhini. Google to see if you agree.

  4. Great article Helen, but I would challenge you on opus palladianum being on of the easier ones. I actually think it’s one of the harder ones to do well and keep a nice even flow, consistent interstices and no distracting grout rivers. 🙂

    1. Thank you Marian! And thank you too for the reminder that palladianum is not at all easy to do well. One of the drawbacks in a sense of well executed mosaics is that they look almost effortless when of course we all know that they’re not. The only one that could remotely be described as ‘easy’ is tessalatum.

  5. Oh…my… goodness! I already cant wait to read this again, Helen. beautiful writing and serious props to you for starting the new names. I knew it was gonna happen soon! Such exciting times we work in..

  6. Julie Sperling

    I love the way you think about and write about mosaic, Helen. Your contribution to the dialogue is invaluable and I always look forward to reading what you write. And I *adore* these additions to our lexicon. “The opus is the mosaic” sounds very McLuhan-esque: “The medium is the message”…

  7. Helen, I loved your article. For me andamento is the soul of mosaic and the state of mind otf the artist. Your mosaics are fantastic.
    Best regards from Colombia , South America.

    Ana Posada Mosaico

  8. Annette Hillsdon

    I really love your andamento article. I struggle with this and it has really helped make it easier.
    Thank you
    Annette Hillsdon

  9. great article, I am taking a master drawing class with 3 artists who do not work in mosaic and although they are polite, think mosaic is something you buy at homedepot then slap on your bathroom walls with thinset

  10. Avril Cornelius

    Better late, then never! I began to try and teach myself how to make mosaics a year ago, during covid, and I fell in love with this art form. I was lucky enough to find a local artist, David Chidgey, who agreed to teach me, and we finished an andamento workshop, just yesterday. After a year of making picture frames, garden stones and flower pots, I knew andamento was necessary for my progress in mosaics. I thoroughly enjoyed your article; and it was interesting and piqued my curiosity even further. I can’t wait to try out some of these techniques. Thank you so much!

    1. It’s so nice to hear that you have fallen in love with mosaics. I warn you, if you aren’t aware already, it does become a real addiction! You are lucky to have such a brilliant teacher nearby. Good luck with your exploration of andamento.

  11. Avril Cornelius

    Helen, I’ve been reading more of your article’s, and your fierce love and defense of mosaics comes shining through each one! Yes, I’m happily addicted to everything about mosaics, from the glass, to the excitement of learning some new technique. I know how lucky I was to find David, who is not only my teacher and mentor, but is also now my friend. He is a very gifted artist, and a terrific teacher. I am currently in the process of moving to another city, and with all of this upheaval, I’m finding it impossible to create anything, and without mosaics, I’m feeling somewhat untethered. Withdrawal, I suppose. But, I am currently writing down your descriptions of the different opuses, and drawing them out. I found some seven inch, glazed ceramic floor tiles. I thought I would cover them with a scratch coat of thin-set, and practice andamento techniques, to help keep me tethered. Helen, can you recommend any books about andamento?

    1. Untethered! A brilliant word, which describes exactly how I feel when I can’t make mosaics too. I’m afraid I am not aware of anything written about andamento but it is worth looking at the Mosaic Arts Online courses by Anabella Wewer and Rachel Sager. They both have classes about andamento which approach it in a different but interesting way which concerns the process of line building. I am currently writing a book and will include a chapter on andamento so that might be of use sometime down the line…Good luck with your house move.

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