The Scott & Bailey star was filming new BBC1 First World War drama The Crimson Field about the life of military and voluntary nurses working on the frontline in which she plays field sister Joan Livesey.
Jones said that authentic looking severed toes and ears were kept in the fridge while they were working on the show to keep them looking fresh.
Set in June 1915 in Northern France the six part drama - which also stars Oona Chaplin, Hermione Norris, Kerry Fox and Kevin Doyle - does not tone down the horrific injuries with which nurses were confronted when treating soldiers wounded in battle.
In the first episode a young Voluntary Aid Detachment comes across lost toes while cleaning used bandages.
Jones revealed: "They used to be kept in the fridge in make-up. So we'd go in to get some milk and there'd be toes and ears.
"The wonderful make-up designers did all the injuries brilliantly. There were teams and teams of make-up girls, there'd be a second make-up van, who were in at the crack of dawn, with all these wonderful supporting artists."
The former Coronation Street star also revealed the lavish lengths the production crew went to to recreate First World War France in a field in Wiltshire, even growing an authentic strain of crop which would have grown a century ago.
Jones confessed: "When I first got the job I thought great I'm going to France, and then no, I got on a train to Wiltshire! But it was beautiful.
"When I got there it was just amazing, where the cemetery was because they planted actual wheat, that had grown 100 years ago. And then we had tents, and the main hospital, so the scale and the depth of what the cameras could catch was absolutely amazing. And add on to that your carts and horses and vintage vehicles.
"We started in summer so we had wasps everywhere, then we went into fields of mud and rain and wind, so our dresses were covered in mud up to here and we went through all that and the set got better and better looking."
Downton Abbey star Kevin Doyle, who plays doctor Lt Col Roland Brett, said the sets were so detailed he felt they could have actually treated patients there.
He said: "Months and months before they planted an allotment for the camp kitchen, it just looked beautiful. And the field of wheat, it's only in one scene, but we're walking by from the cemetery and there were two or three guys scything the wheat, Just for that moment they planted it months in advance.
"When you went into a pharmacy or the wards the level of contribution from the art department was extraordinary. Everything was there that you need. If we were trained doctors we could have taken people in!"
Hermione Norris, who plays Matron Grace Carter, told how the show had felt like a personal way of remembering all those who lost their lives in the war, and she hoped viewers would feel the same.
"I've always had a passion about World War One, an absolutely fascinating period of history, a time of huge social change for women in particular," she said.
"For me it's a generation I remember. I remember the smell of that generation, the attitude of that generation and the scale of loss and devastation is beyond comprehension.
"I became interested about 20 years ago and read the Pat Barker trilogy and went to Flanders.
"And just the psychological impact on us as a nation, I think we're still living the consequences of.
"It was from my point of view a small act of remembrance every day, at the going down of the sun and in the morning. 'We will remember them'. And we really did feel that there. And I hope for people watching on a Sunday night it's a small act of remembrance."
The original six part drama was written by Sarah Phelps, who adapted Great Expectations for the BBC in 2011.
The Crimson Field is due to be broadcast on BBC1 on Sunday evenings from next month.