In 1845, he received a bursary from the city of Rennes and travelled to Paris where he worked at a studio together with a Rennes sculptor called François Lanno.
He then worked at the studio of François Rude.
In around 1850 he settled back in Rennes and started to specialise in church furnishings.
His works are numerous and can be seen throughout Ille-et-Vilaine.
His first masterpiece was the pulpit erected in the Église Sainte-Croix à Saint-Servan, a suburb of Saint-Malo).
This had been promoted and funded by Napoleon 111 during his visit to Brittany in 1858.
During this visit, the church's curate, Monsieur Huchet, had brought the church to the Emperor's attention, highlighting the fact that it lacked furnishings.
The Emperor was generous and the pulpit was the result.
Jean-Marie was assisted by his brother Antoine, as was often the case, and the pulpit was indeed signed "Valentin Frères, Architectes et sculpteurs".