The violin labelled "David Christian Hopf, musicus" and dated 1760 was recently restored at my studio. The maker belongs to the dynasty of makers originating in Klingenthal and founded by Caspar Hopf (born in 1650 in Graslitz, Czech republic). The dynasty consisted of about 42 makers with
David Chirstian the young being the most sought after (1734-1803). Hopf makers were active well into the 19th century.
The model is remarkably square and somewhat clumsy and was apparently assembled without the use of mold - the practice generally followed in the more southern regions of Germany, such as Füssen.
The instrument was accidentally dropped on the floor which resulted in two bass-bar cracks at a distance of approximately 3 mm one from another, with one of the cracks extending to the eye of the f-hole and another ending near the end of the tailpiece. The ribs at the lower block came loose from the block, three of the four corners came loose with the ribs partly detaching from the blocks, and most of the old cracks, totalling ca.30cm went open as a result of the accident.
Restoration work lasted about 100 hours and involved bleaching old cracks with various chemical solutions (hydrogene peroxide and chlorine bleach, oxalic acid - with consequent neutralising by sodium bicarbonate and sodium percarbonate), levelling one of the bass-bar cracks - the longest one, gluing cracks and fixing them with cleats, doubling the areas of the upper and the lower blocks where the wood was fractured and lost as a result of previous openings of the instrument (probably two openings). The cracks which showed some loss of wood along the edges have been filled with sandarac filler and retouched with clear varnish which successfully rendered them virtually invisible. The area under the bridge was cleaned with soapy alcohol/water mixture to remove the thick build up of rosin. N.B. If you are a player, it is unlikely that you understand the processes described here above or have enough experience. It is not recommended for to you to try any of these out on your instruments.
Given the fact that original bass-bars are extremely rare and represent valuable information on the practices of violin-making in the 18th century - in Germany in this case - I considered it important to preserve it and glue the bass-bar cracks without removing the bass-bar.
You can probably note the darkened area in the left lower bouts. Staining was caused by greasy or waxy cleaning liquid which seeped through the cracks which were not tightly closed. De-greasing this area in order to glue the cracks and fit the cleats was an unpleasant complication and could have been easily avoided if musicians would rather use dry soft cloth to wipe the instrument clean rather than any of the "safe" commercial cleaning liquids.
The neck and the upper block are not original. The nails and the baroque neck were nicely made by someone whose name I do not know in the more recent years. The block area shows another curious detail: the flat area protruding from under the modern block proves that the neck was made from one piece of wood with the block, as this was customary with the Flemish and South German violin-makers in the 17th-18th centuries and with the Hopfs of course.
The instrument has a nice sound though it is not particularly big. The body has serious overal deformations obviously due to the extreme thinness of the plates.