Violence in B.C. prisons is on the rise, says the union representing jail guards, which is calling for more staff to handle the increased number of attacks behind bars.

One of the most troubling attacks is the use of molten butter as a weapon to burn other inmates, said Dean Purdy, a spokesman for the union representing prison guards.

"They're heating up butter mixed with sugar and bleach in the microwaves to extreme temperatures and throwing it in the face of their targeted inmate." said Purdy, a vice president at the B.C. Government Employees Union.

"It's heated up for sometimes 10 or 15 minutes to the most extreme temperatures where it's just bubbling.

"If it hits someone in the face, it actually will offer such severe burns that the face starts to disfigure or almost melt."

Some inmates have been permanently disfigured by these attacks.

Attacks rising, says union

The B.C. government has responded by limiting prisoners' use of microwaves, the CBC has learned.

But Purdy said more guards are needed to intervene before prisoners are attacked.

The butter attacks are part of an overall rise in violence in B.C. prisons, he said.

According to numbers gathered by the union, attacks on both guards and inmates rose more than 30 per cent last year, from 978 attacks in 2014 to 1,394 attacks in 2015.

Attacks by inmates on staff rose from 71 in 2014 to 99 in 2015, according to the union.

In one case, which was cited in a criminal court case, an inmate seated at breakfast was attacked by another inmate who hurled a container of melted butter at him. The victim suffered second-degree burns on his face, neck, and lips and swollen eyes.

In a victim impact statement, the inmate said the attack left him nervous and depressed.

Lawyer Tonia Grace, who has represented one injured prison inmate, said removing prison microwaves is not the answer.

"The microwaves provide a semblance of normality and independence to these people so they can, you know, feed themselves," Grace said. "You don't get large portions in custody. You get like airline food. You're getting that 24/7."

"So lots of these people will buy their own snacks to try and supplement their diet and try and cope with the fact that they've had their liberty taken away from them."

'Scalding' butter used as weapon

The hot butter attacks came to light following a WorkSafeBC inspection conducted at the Prince George Regional Correctional Centre last October.

That report found that inmates there were using microwaves to heat butter and other condiments "to a scalding temperature and using the mixture as a weapon against staff."

Purdy, who is also a guard at Vancouver Island Regional Correctional Centre, said more prison staff would reduce the risk of attacks. In B.C., there was once a minimum requirement of one guard for every 20 inmates, he said.

Now, in some facilities, that ratio is much higher. For example at the Surrey Pretrial Centre, there is one guard for every 72 prisoners. At the Prince George prison, it's one guard for every 40 prisoners.

"These spikes are something that go hand in hand with overcrowding, with capacity pressures in the jails, and it's a big concern for us ... because safety is paramount in our business," Purdy said.

B.C. Solicitor General Mike Morris said in a statement that the potential for violence in B.C. prisons is an unfortunate reality "given the violent criminal histories of many in custody."

Morris said the ministry has hired 440 new staff since 2007, and a new correctional centre will soon open in the Okanagan to address crowding.

In a background statement provided by the ministry, it said that staff-to-prison ratios are not all as bad as Purdy suggests, stating they're as low as one guard for 10 prisoners in some units.

Last year, B.C. Auditor General Carol Bellringer issued a report that said the province's prisons are overcrowded, endangering inmates and staff.

With files from the CBC's Daybreak North.

To hear the full story listen to the audio labelled: Molten butter attacks in B.C. prisons prompt demands for more guards.