The 15th and 16th century Italians regarded the picture frame not merely as an adjunct to a painting but as an architectural endeavor in its own right. In illustration of this, the Florentine style mimics the statics of a building while the Venetian style is based on the concept of dominance of the overshadowing ornamentation. The Florentine use of architectonic framing (architecturally based elements with occasional additions of plant-form components) stands as the source of all succeeding picture framing designs. Even with Italy's regionally artistic independence, a progression of Italian picture frame evolution can be discerned.

Aedicular Frames

With the flowering of Renaissance architecture and interior decoration, the picture frame took on a fully classical form as evidenced by--the aedicula or tabernacle frame for altarpieces or devotional paintings and the corresponding cassetta frame for secular works. Although the portrait frame developed from the simple structure of the earlier rectangular altarpiece, it was still bound to the Gothic and Renaissance version by a common ornamental language. This soon changed: carvers, gilders and artists - whoever worked on the frame - used every available type of decoration to enrich the setting of the paintings, and so produce an approximation of the celestial world.

Cassetta Frames

The earliest portrait frames are of the cassetta or architrave type. These consist of a decorative frieze between two mouldings formed of small fillets, astragals, hollows and ogees. One of the oldest forms of ornamentation for the central frieze is a continuous run of scrolling or undulating foliage. The chief techniques for the panel decoration of these Renaissance frames were applied gesso (pastiglia), stucco, punched work (bulinatura), painted or scraped (sgraffito) decoration, and relief carving into the wooden base. Tondo Frames Concurrently with oblong frames, a particularly Tuscan form of setting developed: the circular frame for painted tondi- frequently representing the Virgin and Child. Rooted in the custom of offering a ''birth tray'' of food and gifts to a new mother, this frame design took on many incarnations. The Della Robbia designed tondi, containing glazed and enameled terra-cotta fruit and flower garlands typifies this style. Tondi continued to be made, although less frequently after the late Renaissance. This method of presentation regained popularity in the 18th century, when oval forms became common for portraits. Compound Profile Frames Beside the cassetta and tondi frames, a number of patterns emerged, combining a diverse selection of enriched architectural mouldings-ogee, convex torus, concave Scotia or cavetto, etc.--each creating different degrees of depth and movement. Revivals of this method (stacking various mouldings containing uninterrupted ornamentation) can be found periodically throughout history and into the present. This development of the compound profile introduces a transitional stage between Renaissance and Mannerist forms, as well as foreshadowing later Baroque patterns.

Mannerist

Mannerism might be interpreted as a variation played on the classical theme. This device is originally, though not exclusively, Italian. It is classicism seen in a distorting mirror, which exaggerates elements of a rational and logical structure into a sophisticated and highly self-conscious style. Working with rich, energetic rhythms and imaginative use of ornamentation, mannerism both enlivened and subverted the classicism of the high renaissance. A superb example of the Mannerist interpretation of the aedicular variety is the Sansovino frame (named for the architect and sculptor Jacopo Sansovino). The robust, theatrical effect of this frame had an enduring appeal and inevitably influenced later designs. A striking silhouette and bold sculptural form, with its occasional parcel gilding, was intended to enhance Mannerist paintings. Their twisted, attenuated forms, their abstract use of line and their brilliant coloring offered designers endless opportunity for improvisation. Auricular Frames The interconnection of Mannerism and the Baroque, with all their oppositions and contradictions, is fully expressed in the Auricular style. This style, a confection of melting cartilaginous and marine shapes, was developed by silversmiths in Holland and Bohemia in the 1620's and, as a frame, is assumed to have been produced into the first half of the 17th century. They would have provided appropriate settings for portraits of the prosperous bourgeoisie; for example, merchants, particularly in Venice and Holland, whose connection with the sea is represented in marine forms. Although in some cases it is possible for a painting to be overwhelmed by the ornamental force of the writhing gilded shape around it, esthetically it should be seen like a precious gem held in a filigree web of gold created by a master goldsmith to protect and enhance it.

Baroque Frames

In contrast to the earlier generation of flat-section cassetta frames--which also continued into the 17th century--these reverse (bolection) profiles project the picture plane forward from the wall surface. The spectator's eye is then drawn into the depth of the picture's composition. Such frames, with their evocation of three dimensions, rich decoration and focusing power, exemplify the Italian Baroque style. The Baroque interiors, for which these frames were designed, expressed the splendor of the 17th century Medici courts. Such patrons saw encouragement of the arts as an attribute of royalty and an enhancement of their prestige. For this reason, and because the Counter-Reformation had hobbled artistic freedom, artists were more in thrall to their patrons than the great Renaissance artists had been. Thus, the latter exerted more influence on the works created for them. The Baroque was nurtured particularly at the papal courts, and the pressure of patronage moved the whole process--and thus the artistic center--inexorably from Florence towards Rome and the Vatican, so that the great paintings of the later Baroque period tend to be Roman rather than Tuscan or Bolognese. As this national focus was moving within Italy, the international focus was moving to France with its growing prominence. This is discernable in the French-derived frame profiles that appeared in northern Italy, where hitherto the direction of the influence had been all but exclusively the other way. Salvator Rosa, or Carlo Maratta Frames Similar to the Louis XIII Piedmontese profile and perhaps the best known of the Italian frame types, this style was the most typical of the Roman Baroque in its richness, symmetry and classicism. Known as both the Salvator Rosa and the Carlo Maratta pattern, it is a severely linear sequence of stepped ogee and convex mouldings around a broad scotia. Periodically termed the ''Roman gallery frame'' (from its use in the 18th century re-framing of the great papal collection); the play of concave and convex surfaces gives a logic and stability to this frame, which make it appropriate for such mass framing projects. It was also suitable because the unembellished version would have been inexpensive to produce. These same factors would influence Napoleon's re-framing decisions for the Louvre. After the linear moulding would have been quickly turned out by mechanical means, the carcass of the frame could then be gessoed and gilded. Seen in quantity, the sequence of rectangles would separate the wall surface into a net-like web of panels, which would not only hold the paintings but would act--through the complimentary curves of each moulding--to catch light and throw it onto the picture surface.

Rococo

This period of transition from the Baroque to the Rococo ended the primacy of Italian art. With the building of Versailles (from 1678), France had now become the center of European art. The totality of style begun in the Baroque period continued with the correspondence between frames, furniture and interior decorations. In Rome, which ignored the Rococo, the classical Maratta continued to be most common. It was in the northern Italy, with its nearness to France, and in the extreme south that Rococo was built upon the tendencies of preceding styles. Soon, French strapwork ornaments and versions of Louis XV frames appeared, but Italian Rococo designs include an original and refined use of this style with carvings lighter than the most delicate French Rococo. In Venice, a variety of distinctive frame styles developed, among them a Chinoiserie frame; the so-called Canaletto frame; and light, asymmetrical designs reminiscent of Mannerist precursors.