Question: What year did Rembrandt start etching?
About the article "Rembrandt", section "Etchings".

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The Three Crosses is an etching and dry point painting created by Dutch artist Rembrandt van Rijn depicting the crucifixion of Jesus Christ.
The subject is Jesus Christ on the cross, flanked by the two thieves who were crucified with him.
The Virgin Mary is depicted weaping and being supported by the Evangelist.
Roman soldiers on horseback and grieving citizens are depicted around the crosses.
Professionals have speculated that the scene might be interpreted as the moment of Christ’s death.
The sky is very dark but pierced by a beam of light that surrounds the figure of Christ, representing God’s light from heaven.
The iconography in the piece is especially intricate.
According to Paul Crenshaw of the Kemper Art Museum, Rembrandt was inspired by the text from when Christ cried out, “My God, why hast thou forsaken me?” Rembrandt drew heavily on biblical sources in his work, as well as being influenced by other Baroque contemporaries.
Rembrandt created over 300 works that were inspired by the Bible.
The piece's etching does not allow for dramatic contrasts of light and shade, known as chiaroscuro.
Rembrandt produced the work in four stages, increasing in each the effects of these contrasts.
Etching and dry point are labor-intensive processes, and one of the early forms of printmaking.
Rembrandt chose these media based primarily on the fact that he was suffering from financial difficulties all the time.
He had to sell many of his etchings in order to be able to afford to print "The Three Crosses".
Rembrandt was able to make around sixty impressions from the plate in its first three stages, the darkest shadows on the piece being done in dry point, and Christ and the lighter figures being etched.
The nature of the media meant that it was possible for Rembrandt to make continuous alterations (which he did over a ten year period), adding further etching and dry point, changing the composition of the picture and making the final image darker and more chaotic: In the last stage, the Virgin Mary has become an almost disembodied head surrounded by darkness, and the figures that originally encircled her have, in consequence, been removed, as have been some of the soldiers on horseback.
A man in a large hat (also on horseback) has been added and is believed to be a figure from Rembrandt’s "The Conspiracy of Claudius Civilis."
The most dramatic alteration is to the "heavenly light" which has become considerably darkened, especially to the right of the picture, by which Rembrandt may be making a clear distinction between the 'good' and 'bad' thieves.
Each progressive change in the work increases the focal importance of the Christ figure.
In its fourth and fifth state, Rembrandt inked the plates in a different number of ways and with different qualities of ink.
One of the prints in the fourth stage is located at the Kemper Art Museum. 
 'Scenes from Genesis', by Marten de Vos [http://www.codart.nl/downloads/Courants/courant10.pdf] 'Annunciation', graphic by Hendrik Goltzius 'Forteress by the river',by Jan van de Velde 'Last Supper',graphic by Sadeler family 'Hearing', by Jan Dirksz Both 'Vision', by Jan Dirksz Both 'Ecce homo', cooper etching by Rembrandt c. 1636 'Self Portrait with hat', graphic by Rembrandt c. 1630 'Portrait of Man', etching by Rembrandt 'Man with bag', etching by Rembrandt c. 1635 'Merchants expulson from the temple', etching by Rembrandt c. 1635 'Old man and boy', graphic by Rembrandt 'Old man with hat and pearls', graphic by Rembrandt 'Self Portrait with toga', etching by Rembrandt 'Self Portarait', graphic by Rembrandt 'Apoteosa', graphic by Peter Paul Rubens 'Old Amsterdam', graphic by Lucas van Leyden 'Death over the city', graphic by James Ensor  
"Joseph and Potiphar's Wife" is a 1634 etching by Rembrandt (Bartsch 39).
It depicts a story from the Bible, wherein Potiphar's Wife attempts to seduce Joseph.
It is signed and dated "Rembrandt f. 1634" (f. for "fecit" or "made this"), and exists in two states. 
During the century after Rembrandt's death the techniques of etching and drypoint brought to their highest point by him gradually declined.
By the late eighteenth century, with brilliant exceptions like Piranesi and Tiepolo, most etchings were reproductive or illustrative.
However, in the 1840s and 50's in France, a number of artists did produce some landscape etchings which seemed to recapture some of the spirit of the old master print.
Daubigny, Millet and especially Charles Jacque produced etchings that were different from those heavily worked reproductive plates of the previous century.
Three people were of special importance to the French Etching Revival: the publisher Alfred Cadart, the printer Auguste Delatre, and Maxime Lalanne, an etcher who wrote a popular textbook of etching in 1866.
Cadart founded the "Société des Aquafortistes" in 1862, reviving the awareness of the beautiful, original etching in the minds of the collecting public.
"A Treatise on Etching" by Lalanne was translated by S.R.
Koehler and published in the United States in 1880.
It played a significant role in the Etching Revival in America.
However, before the translation of Lalanne's book, Philip Gilbert Hamerton had become an enthiusiastic promoter of etching in Britain.
His "Etching and Etchers" (1868) was more an art history than a technical text but it did much to popularize the art and some of its modern practitioners.
The book went through many editions till the 20th century.
By the 1870s Hamerton was also publishing an influential periodical, titled "The Portfolio", that published etchings in editions of 1000 copies.
For Hamerton and others, the father of the British Etching Revival was Francis Seymour Haden, the surgeon etcher, who, with his brother-in-law, the American, James Whistler, produced a body of work starting around 1860 that still stands as one the highpoints of etching history.
Haden was a collector and authority on the etchings of Rembrandt and it comes as no surprise that as Whistler, the younger man, began to show signs of veering far from the 17th century model, Haden and he parted company.
It was Whistler who convinced the artist Alphonse Legros, one of the members of the French Revival, to come to England as a teacher.
This linking of the art of the two countries, though short-lived, did much to validate etching as an art form.
Very soon, French etching would show the same modernist signs that French art showed generally, while English and American etching remained true to the kind of technical proficiency and subject matter artists revered in Rembrandt. 
 Nicholas Poussin – "The Death of Germanicus" Rembrandt – "Rembrandt's Mother: Bust" (etching) Francisco de Zurbarán – "Saint Serapion" Cornelis van Haarlem – "The Judgement of Paris" (approximate date)