How Painting Works | Underdrawing — The Hidden Drawing beneath the Paint

A finished painting can look inevitable.

The hand is exactly there.

The head turns at exactly that angle.

The architecture fits.

The horizon seems settled.

Then infrared light looks underneath.

Another hand appears.

A face was lower.

A fold continued where the painter later covered it.

Dotted lines reveal that the design was transferred from paper.

A confident finished image turns back into a sequence of decisions.

Underdrawing is painting before painting becomes fully visible.

Quick Read

This article owns one specific layer:

the preparatory drawing made on the prepared support before or during the earliest stages of painting.

The National Gallery defines underdrawing as the preliminary outlining of a composition on a primed support, used as a guide while later paint layers are applied. National Gallery: Underdrawing

Its neighbouring owners remain separate:

Grounds and Priming owns the prepared interface beneath the drawing.
Copying owns learning and transmission by repeating other works.
Restoration owns later treatment and conservation decisions.
The Invisible Museum owns the museum-wide technical-analysis and conservation infrastructure.

A useful underdrawing model is:

idea → preparatory study/cartoon → transfer or freehand drawing → adjustment → paint → hidden evidence → technical imaging

Infrared reflectography is especially useful because infrared radiation can pass through some paint layers until it reaches something that absorbs it. Carbon black absorbs infrared strongly, so black underdrawing on a light ground can become visible even when later paint hides it. National Gallery: Infrared

But there is an important caution from the beginning:

infrared reflectography reveals some hidden drawings extremely well; it does not reveal every possible underdrawing equally well.

Material, wavelength, overlying paint and contrast all matter.

The One-Sentence Answer

Underdrawing works by placing a preliminary design on the prepared support—freehand or transferred from another drawing—so composition, proportion and major forms can be organised before later paint hides some or all of the plan, leaving material evidence that technical imaging can sometimes recover centuries later.

1. Underdrawing Comes after the Surface Is Prepared

Support first.

Ground or priming where the painting system needs it.

Then drawing.

This sequence matters because underdrawing is not simply any drawing associated with a painting.

A sketch on loose paper may be preparatory.

Underdrawing is the design placed on the painting support itself beneath later paint.

2. The Hidden Drawing Can Be Extremely Simple

Head oval.

Shoulder line.

Horizon.

Hand position.

The underdrawing does not need to be a beautiful finished drawing.

Its job can be purely operational:

put the important things in the right places before colour makes correction more expensive.

3. It Can Also Be Highly Elaborate

Contours.

Hatching.

Shadow notation.

Landscape details.

Architectural lines.

Some painters solved a large portion of the composition before colour began.

Underdrawing can therefore range from coordinate system to near-complete monochrome design.

4. Freehand Underdrawing Preserves Direct Decision-Making

Draw directly on the panel.

Move the shoulder.

Try another contour.

The drawing records the artist thinking at full painting scale.

Freehand underdrawing can be exploratory rather than merely reproductive.

The support becomes a place to continue inventing.

5. Transferred Underdrawing Solves a Different Problem

The composition already exists on paper.

Now it has to arrive accurately on the panel, canvas or plaster.

Transfer reduces the need to redesign at final scale.

It is especially useful for:

large compositions;
repeated workshop designs;
carefully proportioned figures;
complex architecture;
commissions requiring approval before painting begins.

Planning moves upstream.

6. A Cartoon Is Full-Scale Planning on Paper

In art history, “cartoon” does not mean comic drawing.

The term comes from cartone, a large sheet of paper.

The National Gallery defines a cartoon as a full-size and usually detailed preparation for a painting, fresco or tapestry. National Gallery: Cartoons

The cartoon lets an artist solve composition somewhere that can still be erased, cut, enlarged, patched or shown to collaborators before the final support is touched.

7. Pouncing Turns a Drawing into Dots

Prick tiny holes along the important contours of the cartoon.

Place it against the painting support.

Dust charcoal or another powder through the holes.

Remove the paper.

A dotted design remains.

The National Gallery calls this process pouncing. National Gallery: Pouncing

8. The Dots Usually Need to Be Joined

Pounced dots are registration evidence, not always the final working line.

An artist or assistant may connect them with brush, pen, chalk or another drawing material.

Raphael’s paintings provide excellent evidence: infrared examination reveals pounced points corresponding with surviving pricked cartoons, then fluid lines joining those marks. National Gallery: Studying Raphael — Drawings and Cartoons

Transfer and freehand refinement can occur in the same underdrawing.

9. Tracing Can Transfer a Design without Pouncing

Place a darkened sheet between cartoon and prepared support.

Follow the contour with a stylus.

Pressure transfers the design below.

The National Gallery describes several tracing methods, including blackened intermediate paper and stylus pressure. National Gallery: Cartoons

The painting can therefore inherit a drawing mechanically without inheriting the paper itself.

10. Incision Can Transfer Structure without a Dark Line

A stylus can press through paper and leave a faint groove in the prepared surface.

The artist can then follow the indentation with paint.

This kind of transfer may be difficult for infrared to reveal because the evidence is physical relief rather than strongly infrared-absorbing carbon.

Not all underdrawing evidence is black.

11. Squaring Changes Scale

Draw a grid over a small design.

Draw a larger proportional grid on another surface.

Copy square by square.

Now a small composition can be enlarged while preserving relative positions.

National Gallery technical studies document grid-based enlargement in Renaissance workshop practice. National Gallery Technical Bulletin: Painting Practice in Milan in the 1490s

Scaling is a geometric problem before it is a painting problem.

12. Registration Lines Help the Cartoon Land in the Correct Place

Centre line.

Horizontal mark.

Architectural axis.

These apparently dull lines help align the transferred design with the actual support.

Raphael underdrawings sometimes preserve ruled registration lines that helped position cartoons. National Gallery: Saint John the Baptist Preaching

Precision often depends on infrastructure nobody sees in the final image.

13. A Cartoon Can Be Followed and Still Be Changed

Transfer the design.

Then move the head.

Change the hand.

Omit a fold.

Raphael’s Saint Catherine preserves precisely this kind of evidence: pounced transfer from a surviving cartoon, followed by freehand adjustment and later painted changes. National Gallery: Saint Catherine of Alexandria

Transfer does not abolish invention.

14. Underdrawing Can Preserve Decisions the Final Painting Rejects

A drapery knot is drawn.

It is never painted.

A face begins lower.

Paint places it higher.

The rejected state survives invisibly.

The finished painting becomes only the last visible vote in a longer internal debate.

15. Underdrawing Can Show How the Artist Thought in Stages

First outline.

Then internal modelling.

Then paint.

Or:

transfer the figure accurately, improvise landscape freely, solve colour last.

Hidden drawings reveal sequence, not merely shape.

They can show which problems were settled early and which remained open.

16. Hatching Can Carry Shadow Information beneath Colour

Contours place objects.

Hatching can indicate turning form and shadow.

National Gallery studies of Raphael note freehand hatching added after cartoon transfer because linear cartoons did not communicate all the chiaroscuro needed for painting. National Gallery Technical Bulletin: Raphael’s Early Work

The underdrawing can therefore carry a preliminary lighting model as well as geometry.

17. Architecture Often Benefits from Specialist Drawing

Perspective.

Repeated mouldings.

Stage-like interiors.

These are high-precision subproblems.

The Met’s French Comedians by Watteau provides a striking example: infrared reflectography reveals preparatory architectural underdrawing probably executed by a specialist architecture painter. The Met: The French Comedians

Underdrawing can therefore expose collaboration that the visible surface hides.

18. Workshop Underdrawing Can Standardise Production

One workshop owns a successful figure type.

The drawing is reused.

A cartoon or tracing transfers it into another commission.

Now several paintings share structural DNA.

The Copying and Collaboration articles own the broader transmission and labour systems.

Underdrawing shows the mechanical interface through which a workshop design enters a specific painting.

19. Reused Cartoons Can Create Families of Paintings

Same Virgin.

Different background.

Same Christ Child.

Different accessories.

Shared transfer evidence can show how workshop templates moved between works.

The National Gallery notes possible cartoon reuse and workshop-drawing combinations in paintings by or associated with Joos van Cleve’s workshop. National Gallery: Workshop of Joos van Cleve, The Holy Family

20. Leonardo’s Hidden Drawings Show Mixed Methods

One section can be transferred.

Another improvised freehand.

The National Gallery’s study of Leonardo’s hidden drawing in The Virgin of the Rocks suggests exactly this mixture: some features appear linked to transferred designs while arm, drapery and landscape passages were drawn more freely and revised. National Gallery: The Hidden Leonardo

Great painters do not need one method per painting.

They can switch methods by problem.

21. Michelangelo’s First Painting Shows Underdrawing as Active Refinement

The Met’s technical study of The Torment of Saint Anthony describes a preparatory drawing in liquid medium beneath the paint, revealed through digital infrared reflectography. The Met: Michelangelo’s First Painting

The drawing does not simply copy a source mechanically.

Contours of wings, limbs and drapery were adjusted.

Young Michelangelo appears to use the hidden layer as a place where imitation becomes reinterpretation.

22. Underdrawing Can Remain Visible without Technology

Thin paint.

Worn surface.

Dark line showing through.

Some hidden drawings were never perfectly hidden.

Others become more visible as upper paint changes with age.

The National Gallery notes both possibilities directly. National Gallery: Underdrawing

23. Infrared Reflectography Does Not Literally See through Everything

Infrared radiation penetrates some paint layers more effectively than visible light.

It is then absorbed or reflected depending on the materials it encounters.

Carbon black is strongly infrared-absorbing.

That makes black drawing on a light ground particularly favourable.

The technology reveals contrast, not magical transparency.

National Gallery: Infrared

24. Carbon Is Excellent for Infrared Contrast

Black chalk.

Charcoal.

Carbon-containing ink.

When placed over a reflective light ground, these can absorb infrared strongly enough to form a dark image in the reflectogram.

The chemical identity of the drawing material therefore affects whether modern viewers can recover it.

25. A Missing Infrared Drawing Does Not Prove No Drawing Existed

This is one of the most important limits.

The underdrawing material may not absorb infrared strongly.

Overlying paint may prevent useful penetration.

The contrast with the ground may be weak.

The drawing may genuinely be absent.

Those possibilities should not be collapsed.

National Gallery technical studies explicitly record paintings where poor infrared penetration makes hidden features difficult to identify confidently. National Gallery Technical Bulletin: Painting Practice in Milan

26. Infrared Photography and Infrared Reflectography Are Not Identical

Infrared photography historically recorded a narrower wavelength range.

Infrared reflectography can work across wavelengths that penetrate a wider range of paint layers.

The National Gallery notes that IRR therefore often reveals underdrawing more effectively. National Gallery: Infrared

“Infrared image” can hide several generations of technology.

27. Infrared Reflectograms Are Often Mosaics

A large painting may be captured in many smaller infrared fields.

Those images are joined into a mosaic.

This creates a useful full-picture view but also reminds us that technical images are constructed records, not direct windows.

Instrument resolution, stitching and contrast processing all shape what scholars inspect.

28. X-Radiography Reveals a Different Hidden World

X-rays interact strongly with materials containing heavier elements.

Lead-rich paint can appear strongly.

Metal nails can appear.

All layers are superimposed in the X-radiograph.

The National Gallery distinguishes this clearly from infrared imaging. National Gallery: X-rays

X-ray and infrared are complementary because they respond to different material properties.

29. Infrared Is Often Better for Carbon Drawing; X-Ray Can Be Better for Heavy-Pigment Changes

Hidden charcoal line?

Infrared may be ideal.

Moved arm painted first in lead white?

X-radiography may reveal it better.

Technical examination is not one super-camera.

It is a set of instruments asking different questions of the same object.

30. Underdrawing and Pentimento Are Related but Not the Same

Underdrawing:

preliminary drawing beneath later paint.

Pentimento:

a change made by the artist during the painting process.

The National Gallery defines pentimento specifically as an artist changing their mind during painting. National Gallery: Pentimento

An altered underdrawing can contribute evidence of changing thought, but not every underdrawn line is a pentimento.

31. Underdrawing and Underpainting Are Different Layers Too

Drawing establishes line, placement and perhaps hatch-based modelling.

Underpainting begins using paint to establish larger value, colour or mass structures beneath later finish.

They can overlap materially when artists draw with a brush and paint-like liquid.

The conceptual jobs remain useful to distinguish.

Underpainting is the next clean layer above this article.

32. Hidden Drawing Can Help Explain Why a Finished Contour Looks So Confident

The painter did not invent the final hand edge in one heroic stroke.

The hand may have been studied on paper.

Transferred.

Adjusted.

Then painted.

Visible confidence can be the final result of invisible preparation.

33. Hidden Drawing Can Also Reveal Uncertainty

Three possible shoulders.

Two hands.

A face moved twice.

The final surface may look effortless because the uncertainty was buried.

Technical imaging restores the cost of certainty.

34. Underdrawing Can Help Distinguish Workshop Process—but It Does Not Authenticate Alone

Transfer method.

Hatching style.

Repeated prototypes.

These can support attribution hypotheses.

But workshops share methods.

Followers imitate masters.

Restoration and later copying can complicate evidence.

Underdrawing should be combined with provenance, materials, paint handling and documentary evidence rather than treated as an artist fingerprint.

35. Technical Evidence Can Expose a Later Imitation

A painting looks Renaissance.

The hidden drawing uses a material or construction method inconsistent with the assumed period.

The National Gallery has documented works where microscopic and infrared evidence helped distinguish nineteenth-century imitation from authentic Renaissance practice. National Gallery: The Virgin and Child with an Angel — Close Examination

Hidden process can challenge visible style.

36. But Historical Artists Also Broke Their Own Habits

No underdrawing visible here.

Extensive underdrawing there.

One portrait carefully transferred.

Another painted more directly.

Technique can vary with scale, commission, support, speed and artistic intention.

Absence of expected method should trigger investigation, not automatic rejection.

37. Digital Enhancement Can Help Us Read—but Can Also Make Evidence Look Cleaner Than It Is

Increase contrast.

Join a mosaic.

Overlay a cartoon.

Technical images become easier to compare.

But processed images should still be understood as records generated through instruments and software.

A crisp digital line does not mean the original hidden mark was equally crisp.

38. Technical Imaging Does Not Replace Looking at the Actual Surface

Visible light shows brushwork and ageing.

Infrared reveals one family of hidden contrasts.

X-ray reveals another.

Microscopy shows local structure.

Cross-sections reveal layer order.

No single view owns the painting.

Technical understanding is strongest when different evidence streams agree.

39. Underdrawing Changes How We Think about “Spontaneous” Painting

A final brushstroke can look effortless.

The composition may have been planned for weeks.

A direct-looking face may rest on a transferred cartoon.

Spontaneity at one layer can coexist with discipline at another.

Preparation does not make expression less real.

It may be what makes expressive freedom possible at the final stage.

40. Practical Laboratory: Draw beneath a Thin Paint Layer

Use an inexpensive primed practice board.

Make a simple charcoal or pencil underdrawing.
Photograph it.
Apply a thin semi-transparent acrylic layer over part of the drawing.
Apply a more opaque layer over another part.
Compare which lines remain visible in ordinary light.

The experiment demonstrates that hidden visibility depends on the relationship between drawing material and overlying paint.

41. Second Laboratory: Transfer a Cartoon Three Ways

Draw one simple shape on paper.

Transfer it by graphite-backed tracing.
Transfer it using a small proportional grid.
For adult or supervised learners, make a simple pounced paper template with safe charcoal dust handling.

Compare:

accuracy;
speed;
line character;
how easy it is to enlarge;
how much freehand correction follows.

You are testing transfer systems rather than artistic quality.

42. Third Laboratory: One Design, Freehand versus Transfer

Draw one object directly from observation on one board.

On another, transfer a prepared drawing of the same object.

Paint both.

Ask:

Which version encouraged more change?
Which produced more confident contours?
Which freed attention for colour?
Which felt more constrained?

Underdrawing method changes the kind of problem the painting stage inherits.

43. A Learning Progression from Primary Years to Advanced Study

Primary years: learn that artists can plan lightly before painting. Compare freehand placement with tracing simple shapes without treating tracing as cheating.

Early secondary: study cartoon, tracing, grid enlargement, underdrawing, transfer and why hidden planning can improve final confidence.

Upper secondary: compare freehand and transferred underdrawings, hatching, workshop reuse, pouncing, registration lines, infrared reflectography and changes between drawing and paint.

Pre-university and adult learners: analyse IRR limits, X-radiographic differences, workshop attribution, technical-image processing, forgery detection, collaboration, surviving cartoons and how hidden planning changes interpretation of artistic spontaneity.

The progression is not “hide a better drawing underneath”.

It is “understand which visual decisions are cheaper and clearer to solve before colour begins”.

44. Parent Guidance: Planning Is Not the Opposite of Creativity

What did you decide before painting?
What changed after colour began?
Would tracing help with this particular problem?
Which parts should stay freehand?
What would happen if the first design became invisible?
Could a museum ever discover it again?

These questions help children see preparation as a creative tool rather than evidence that the final work was less spontaneous.

45. How to Look for Underdrawing in a Museum

Does the label mention infrared reflectography?
Was the design freehand or transferred?
Can pounced dots be seen in technical images?
Does a surviving cartoon exist?
Were contours changed after transfer?
Is hatching used beneath painted shadows?
Do underdrawing and finished paint agree closely?
Is there evidence of specialist collaboration?
Does infrared fail to reveal a drawing—and what limits might explain that?
What does X-radiography reveal that infrared does not?

Then ask:

which decision did the artist make before I was ever supposed to see the painting?

46. The Reader’s Underdrawing Map

Prepared support → ground or priming beneath the drawing.
Freehand → design drawn directly at painting scale.
Cartoon → full-size preparatory drawing on paper.
Pouncing → pricked design transferred as dots.
Tracing → stylus or transfer layer copying contours.
Squaring → grid-based enlargement or reduction.
Registration → alignment lines placing the transferred design accurately.
Hatching → preliminary modelling or shadow notation.
Revision → differences between underdrawing and final paint.
Infrared reflectography → imaging technique especially effective for certain carbon-rich hidden drawings.
X-radiography → complementary method responding strongly to heavier elements across the layer stack.
Limit → no visible IR underdrawing does not automatically prove no underdrawing existed.

The next clean Painting layer sits directly above this one:

after the drawing is placed, how does the painter establish the first painted masses of light, dark and colour before the final surface?

That is a separate future article: “How Painting Works | Underpainting — The First Painted Structure beneath the Visible Colour.”

Frequently Asked Questions

What is underdrawing in painting?

Underdrawing is preliminary drawing placed on the prepared painting support before later paint layers. It can guide composition, proportion, major contours and sometimes shadow structure.

How do museums see drawings hidden under paint?

Infrared reflectography is one important method. Certain paint layers transmit infrared radiation while carbon-rich drawing materials absorb it strongly, allowing hidden lines to appear in an infrared reflectogram.

What is pouncing?

Pouncing transfers a drawing by pricking small holes along its contours and dusting charcoal or another powder through those holes onto the painting support, leaving a dotted outline that can then be joined or refined.

What is the difference between underdrawing and pentimento?

Underdrawing is the preliminary drawing beneath paint. A pentimento is an artist’s change of mind during the painting process. A changed underdrawing can provide evidence of revision, but the terms are not interchangeable.

Does infrared always reveal underdrawing?

No. Visibility depends on the drawing material, ground, overlying pigments, wavelength range, equipment and contrast. Failure to detect underdrawing is not automatically proof that no preparatory drawing was used.

How is X-radiography different from infrared reflectography?

Infrared reflectography depends on infrared absorption and reflection, often making carbon-based underdrawing visible. X-radiography depends strongly on how materials absorb X-rays, especially pigments or structures containing heavier elements. The two methods reveal different aspects of a painting.

Sources and Further Reading

The Idea to Keep

A finished painting shows what survived.

Underdrawing can show what came before survival was decided.

The first position.

The transferred design.

The abandoned hand.

The registration line.

The freehand correction.

Paint hides many of those decisions.

Technical imaging lets us recover some of them.

And suddenly the masterpiece is not an answer anymore.

It is a record of questions the artist once had to solve.