Inventories

6 Months Ended

Jun. 26, 2020

Inventory Disclosure [Abstract]

Inventories

Inventories

Inventories on the Consolidated Balance Sheets are summarized as follows:

	June 26,		December 31,
(Thousands)	2020		2019
Raw materials and supplies	$	54,720	$	35,612
Work in process	172,678		177,780
Finished goods	30,304		25,506
Subtotal	$	257,702	$	238,898
Less: LIFO reserve balance	47,855		48,508
Inventories	$	209,847	$	190,390

The liquidation of last in, first out (LIFO) inventory layers increased cost of sales by $0.1 million in the second quarter and first six months of both 2020 and 2019.

The Company maintains the majority of the precious metals and copper used in production on a consignment basis in order to reduce our exposure to metal price movements and to reduce our working capital investment. The notional value of off-balance sheet precious metals and copper was $333.9 million as of June 26, 2020 versus $309.3 million as of December 31, 2019.