This is but a summary of my research over the last 4 years.

Pearl embroidery was viewed as separate form of embroidery sometimes even being placed in a separate guild (Drury, pg. 191 & 219). It was also considered to be more difficult than regular embroidery and done by professionals. (Edwards, pg 61) Lesser quality pearls were primarily used for embroidery. (Edwards, pg 56) Fresh water pearls came from the rivers of Bohemia and Saxony and were used freely throughout central Europe during the Middle Ages. (Drury, pg 268-9)

"The sixteenth century saw throughout Europe a great upsurge of elaborate embroidery on fashionable dress, a trend which was naturally shared by these countries of central Europe with western affiliations. In Poland, at this time, the ready availability of freshwater pearls ensured that they were used not only on church embroidery but also inimmense quantitites on the cress of the court and the aristocratic classes. This type of embroidery was exclusively the work of professionals, always men, who were sometimes decribed as "stringers of pearls" rather than "embroiderers." (Drury, pg. 291)

Pearls were either couched down, first being strung on silk cord, or individually sewn down. In Russian embroidery, the couched thread was also knotted between pearls. (ibid)

Pearl (and coral bead) Size:
Few pearls remain on extant garments. Many of the pearls were repurposed as the expense increased and the availability decreased during the Middle Ages and Renaissance. Mrs. Christie notes “Both large and seed pearls were plentifully used; the latter were lavished in thousands on embroideries, especially on orphreys, borders, and hoods of vestments. The words cum frixio ad pearls are common occurrence in inventory descriptions, although it is now hard to find more than a dozen or two pearls in place….” (Christie, pg. 21).

There are few pearls remaining on items of clothing. Of these the Palermo clothing is the best defined. The pearls on the mantle and the dalmatic are approximately 2 - 2.5 mm in size. The Virgin's Cope from the Order of the Golden Fleece (mid-15th C.) has both seed pearls embellishing various parts (Staniland pg. 44) and appliqued circles of pearls in the shape of a flower. These pearls are a bit larger; in the 2 - 2.5 mm range.

The late 16th/early 17th C. chasuble at the Art Institute of Chicago, item number 1965.773, is covered in coral beads. On MedievalBeads.com, Jean Segrest identifies the coral beads as being equivalent to a size "08" or "06" or "E" bead. An "08" (sb 8/0) is 12 beads to the inch or approximately 2 mm with an 0/6 being 6-7 beads to the inch; being approximately 3 mm.

Seed pearls were used on gloves and purses in the 15th/16th C. There are a number of them in the collections of The Worshipful Company of Glovers of London. The Minden Mitre (c. 1400) is heavily encrusted with tiny seed pearls (picture Staniland, pg. 48).

It is difficult to determine pearl size from paintings. What is very clear from looking at the multitude of paintings is that all sizes of pearls were used and frequently multiple sizes to get the requisite level of detail.

Pearls in Paintings and Portraits:
The focus for my projects is late 15th/early 16th C., primarily German, and the notes below are reflective of this. Nor is the list below exhaustive, but rather more representative of how common pearl embroidery was during this era.

National Gallery of Art Washington by Walker ISBN 081098148-3
Pg. 162-3 Cranach – the Elder – Prince of Saxony c 1517

Milla Davenport, The Book of Costume ISBN -517037165
Pg 339 Life of ST Godelieve XVc Flemish – Bishop – cope with border of pearls (Met)
Pg 392 Cranach – 3 women 1525-30 Vienna Museum Art
Pg 403 – portrait of a Woman – Unknown Saxon Artist c. 1548

Francois Boucher, 20,000 Years of Fashion ISBN 0810916932
Ppg. 241 – Cranach – Woman with a Hat c 1525 Frankfurt Stadelsches K
Pg. 245 – Cranach – Portrait of Sybilla of Cleves, Weimar SK
Anon, Portrait presumed to be Eliz, daughter of Gustavus I, c 1590 – headdress of pearls, Gripsholm Castle Sweden

The Painting of Hans Holbein the Younger by Paul Ganz  1950
1522 – Altar of Johann Gerster, Basle (see bishops mitre) – pg 47, detail pg 48
1527 – William Warham, Bishop of Canterbury – pg. 82, detail mitre pg 84
1528/9 – Altar piece with Madonna of Mercy and Mayor Meyer’s family -- pg. 91 Anna Meyer bridal crown, pg 92 Magdalena Meyer bodice front
1537 – Henry VIII  pg 137
1536 – Jane Seymour  pg 138
1539 – Henry VIII pg 147
1539 – Anne of Cleves pg 148
1542 – Henry VIII – pearl embroidery – pg. 158 – detail on 159-60

Gothic and Renaissance Art in Nuremberg 1300-1550 Metropolitan Museum of Art ISBN 0870994662 -- a variety of stain glass windows – Bishops with mitres with pearls 1510-5

The Thyssen-Bornemisza Collection Early German Painting 1350-1550 by Isolde Lubbeke ISBN 0856673765
Pg 44-5 Portrait of a Woman wearing the Order of the Swan, Anon Master active at the court of Ansbach c. 1490
Pg 48 Franconian master 1500 with Countess Sophie of Poland and the daughters of Margrave Albrecht Achilles from The Virgin sheltering Supplicants under her Cloak – reverse of alterpiece in the Schwanenenordens-Ritterkapelle in St Gumbertus, Ansbach
Pg 44- 49 – references to Ursula Gerkin, -- embroidered oak leaves,  notes on costume including reference to single sleeve work and pearl embroidery – Swabian.
Pg 110-115 Diptych with syhmbols of Mary’s Virginity and Christ’s Act of Redemption by Anon M active in Westphalia in the early 15^th C – Mary’s crown of pearls and pearl trimmed dress “ mark the Mother of God as queen”
Pg 132-135 Hans Baldung Grien  Portrait of a Woman 1530 – pearl decorated caul and collar    -- commenting similarity to Cranach's Judith
Pg 135 Cranach – Judith 1530 – pearl caul and collar
Pg. 154 Anton Beurer, Portrait of a Woman  - late 15^th C – twisted band of gold and pearls – BUT in front of headdress/haub
Pg 156-161 Jorg Berg the elder: Portrait of Coloman Helmschmid and his Wife Agnes Breu 1500-5  band of pearls on wife’s head piece in front of hat
See also Thoman Burgkmair, Wedding Portrait of Jakob Fugger and Sibylla Artzt 1498 – pg 161 (right sleeve pearl embroidery)
Pg 166-171 Barthel Bruyn the Elder -- Pair of Portraits of a Man and the Patrician Family of Weinsberg and Portrait of a Woman c 1538/9 Band of velvet with pearls on her hat and pearl rosettes on dress frontice
Pg. 178-193 Han Cranach Hercules at the Court of Omphale 1537 – 3 ladies 2 with beaded/pearled cauls
Pg. 187 see also Lucas Cranach the Elder Hercules at the Court of Omphale 1532 (lost – WWII) dress of one lady pearled
Pg 190-213 Lucas Cranach the Elder -- Salome 1510 – pearled headdress;
Also 4 wing paintings 1514 – donor portraits – his with pearled caul and front piece, hers with band of pearls (Duke George and Duchess Barbara of Saxony)
Pg 214-7    Lucas Cranach the Younger -- Portrait of a Woman 1539 – pearled caul and neckband, Anna von Minckwitz 1543 – hat similar to Anne of Hungary – could be pearls and bullions, pearled caul
Pg 242- 9  Hans Holbein the Elder -- Portrait of a Woman in Profile 1518/9 – pearl embroidered band around hair
See alsoVarious portraits of Henry VIII
Pg 255 Francis I by Jean Clouet 1525
Pg 298-301 Hans Maler Portrait of Anne of Hungary and Bohemia 1519 – hat with very large pearls
See also woodcut by Maler and 2 woodcuts by Erhard Schon – Maria of Castile and Anne of Hungary/Bohemia 1519 with similar hats

Lucas Cranach by Friedlander and Rosenberg ISBN 1555214754  -- catalogue of info on each portrait – pgs not noted
Ref 301 Portrait of Three Young Women – bodice fronts, cauls, neck and head bands with pearls 1530
& 1530- The Princesses Sibyl, Emily and Sidonia of Saxony – pg 128
Ref 326 Portrait of Margrave George the Devout of Brandenburg-Ansbach – bodice front  1529 – pg 133 (husband of Emily)
Ref 13 – Triptych Martyrdom of St Catherine – Right Wing St Dorothy, Agnes and Cunigunde – Dorothy bodice, Cunigunde headdress  1505
Ref 19 – Portrait of John the Steadfast – 2 bands of pearls on hat and pearl decoration on shirt and bodice and sleeves (Pin of gold and pearls)  1509
Ref 21 – Martyrdom of St Barbara – bodice and sleeves  1510
Ref 23 – Portrait of Dr Christoph Scheurl – front piece and caul  1509
Ref 32 – Salome – headdress and necklace  1510-12
Ref 37 – Virgin and Child with Four Female Saints – bodice and sleeves of virgin 1512-14
Ref 55 – Lucretia – sleeves  1512-14
Ref 85 – Virgin and Child with Sts Catherine, Dorothy, Margaret and Barbara – dress, bodice, necklace  1516
Ref 123-4 Portraits of Prince and Princess of Saxony – headband and shirt on him, sleeves on her  1516-18
Ref 128 – Portrait of Anna Buchner – bodice, headdress  1518
Ref 129 – Jesus and Woman caught in Adultery – her bodice  1520
Ref 132 – Christ taking Leave of Mis Mother – watcher’s headdress  1520
Ref 135-8 – Virgin Glorified – headdresses , bodice, pearled gollar 1520/4
Ref 164 – St Helena Pearl necklace and headdress, caul?  1525
Ref 167 – St Barbara seated before a Green Velvet Door – bodice (diamond pattern)  1525
Ref 171 – Portrait of a Young Lady – caul and necklace  1525
Ref 176-7 – Portraits of an Unidentified couple – bodice and caul (diamond pattern)  1526
Ref 178 – Portrait of a Young Lady holding an apple – caul and bodice?  1527
Ref 220 – Feast of Herod – caul and bodice  1531
Ref 231 – Judith – caul and headband  1530
Ref 234 – Salome – caul and headband  1530
Ref 273 – Hercules with Omphale – bodice  1532
Ref 272, 274, 275 – Hercules with Omphale – headband  1532
Ref 282 – Ill matched lovers – bodice and caul  1531
Ref 284 – Ill matched lovers – headdress and band  1530?
Ref 297 – Portrait of a young lady holding a bunch of grapes – caul, band, ?Trim  1528
Ref 302 – Portrait of a young woman --- caul, bodice front, sleeves, bodice side bands  1530
Ref 303 – Portrait of a young woman – caul and bodice – diamond pattern  1530
Ref 304 – Betrothal portrait of John Frederic the Magnanimous – head band and neck band  1526
Ref 305 – Betrothal portrait of Princess Sibyl of Cleves – head wreath of pearls  1526
Ref 309 – Portrait of a Lady – bodice front, caul, headband  1526
Ref 326 – Portrait of Margrave George the Devout of Brandenburg-Ansbach – front piece  1529
Ref 327 – Portrait of Margravine Hedwig – collar  1529
Ref 329 – Portrait of Prince of Saxony – wreath with added pearls  1529
Ref 337 – Portrait of Electress Sibyl of Saxony – bodice, caul with band  1535
Ref 347 – Portrait of a Lady – bodice, decoration on chemise, headband, caul  1534
Ref 348 – Portrait of an Aristocratic Saxon Lady – caul and neckband  1534
Ref 349 – Portrait of Christiane von Eulenau – caul  1534
Ref 362 – Christ Blessing the Children – lady center with caul and embroidered gollar   1538
Ref 420 – Female Portrait – hat, caul, headband, bodice 1540

Die Gemalde des 16. Jahrhunderts – Germanisches Nationalmuseum Nurnberg ed. Locker ISBN 3775706968 [note many instances where pearls are possible but only confirmed are noted – book is in German]
Pg 94-5 Bartholomaus Bruyn 1530 altar frontal – patrons woman headdress and man headband
Pg 105 gm 877 altar piece – side panel one of the ladies bodice and headdress by Bruyn Bartholomaus
Pg 140-1 Lucas Cranach - #218 – old man with younger woman – bodice
Pg 144-5 Lucas Cranach #217 – young woman – caul and bodice 1530 also see Salome in Budapest museum
Pg 150-3 Lucas Cranach #1108 1534 cauls and bodice
Pg. 158/9 Lucas Cranach #210, 211 Passion of Christ – cauls
Pg 238-9 M of Further Hochaltar 1510 #195 woman in gollar
Pg 241-3 M of Habsburger 1507/8  #332  - woman with sleeves and bodice pearled

Conversations on the Dresden Gallery, by Aragon & Cocteau ISBN 0841907307
Pg 36/7 Cranach – The St Catherine Altarpiece – all 3 panels in color 1506. Left – Sts Dorothy, Agnes and Cunegund. Dorothy – bodice, Agnes sleeves maybe, Cunegund headdress, edging on bodice and sleeves – pearl band 3 deep. Main panel – Catherine sleves and bodice. Right –  Sts Barbara, Ursula, Margaret – all 3 have pearled bodices and sleeves
Pg 38 Cranach – Presentation at the Temple. Bishop – banded with pearl decoration, priest with neck band, and courtier possible cloak with pearl or other embroidery. Possible gollar on right woman.

Groeningemuseum Bruges by Dirk de Vos. The Complete Collection 1984
Pg 12-13 Van Eyck – Madonna with Canon  1436 – vestments with borders of pearls

The Women of the Renaissance by Hannelore Sachs 1971
Pg 76 Anna Electress of Saxony – pearl encrusted headdress
Unknown saxon master 16^th C. pg 57

Additional Bibliography:

A Pictorial History of Embroidery, by Schuette, Marie & Sigrid Muller Christensen 1964
Beadwork by Pamela Clabburn – Shire 57 ISBN 085263529X
English Medieval Embroidery by AGI Christie 1938
The History of Beads: from 30,000 BC to the Present by Lois Sherr Dubin ISBN 0810907364
Il Piviale Di Pio II by Laura Martini ISBN 8882153266
Medieval Craftsmen: Embroiderers by Kay Staniland ISBN 0714120510
Needlework: an Illustrated History, edited by Harriet Bridgemen and Elizabeth Drury ISBN 0709200455
Nobiles Officinae (Palermo 12^th 13^th C robes) ISBN 3854970765
Textile Conservation and Research by Flury-Lemberg – Abegg ISBN 3905014025