Almost all the vases in the museums of Europe have been mended, and the most skilful workmen at Naples and Rome were employed to restore them to their pristine perfection. Their defective parts were scraped, filed, rejoined, and supplied with pieces from other vases, or else completed in plaster of Paris, over which coating the restored portions were painted in appropriate colours, and varnished, so as to deceive the inexperienced eye. But either through carelessness, or else owing to the difference of process, the restorations had one glaring technical defect: the inner lines are not of the glossy hue of the genuine vases, and there is no indication of the thick raised line which follows the original outline in the old paintings. Sometimes the restorer pared away the ancient incrustation, and cut down to the dull-coloured paste of the body of the vase. Sometimes he even went so far as to paint figures in a light red or orange oil paint on the black ground, or in black paint of the same kind on orange ground. But in all these frauds the dull tone of colour, the inferior style of art, and the wide difference between modern and ancient drawing and treatment of subjects, disclose the deception. The calcareous incrustation deposited on the vases by the infiltration into the tombs of water, containing lime in solution, can be removed by soaking the vases in a solution of hydrochloric acid.[65] In other cases vases with subjects have been counterfeited by taking an ancient vase covered entirely with black glaze, tracing upon it the subject and inscription intended to be fabricated, and cutting away all the black portions surrounding these tracings, so as to expose the natural colour of the clay for the fictitious ground. When red figures were intended to be counterfeited, the contrary course was adopted, the part for the figures only being scraped away, and the rest left untouched. Vases, indeed, in which the ground or figures are below the surface should always be regarded with suspicion, and their genuineness can only be determined by the general composition and style of the figures, and by the peculiarities of the inscriptions. The latter also are often fictitious, being painted in with colours imitating the true ones, and often incised; indeed, nearly all inscriptions incised after the vase has been baked are liable to give rise to suspicion. The difference of style in the composition of groups, and especially small points in the drawing, such as the over-careful drawing of details, the indication of nails, and various other minute particulars, are also criteria for detecting false or imitated vases. Water, alcohol, and acids will remove false inscriptions, but leave the true ones intact.