The best way to test the market would be to start with direct mail to lists of business decision-makers in California and neighboring states. Start with a clear target audience in mind--from the type and size of business that could buy from you to any other special qualifying criteria that would make a business a good prospect. 

Then contact a list broker in California and provide this information, as well as the title of the individuals (purchasing director, vice president, president, etc.) who can make a purchase decision. The list broker will search for the best lists for your purpose and will generally be compensated by a commission from the list vendors or a modest fee.

I suggest you send a letter with a brochure that pictures your factory and makes your pitch "real" for the recipient. Also, be sure to have a great website in place. Business prospects will spend a lot of time there to validate their impressions of your company.

Once you have determined this to be a solid marketing course, I suggest you advertise in trade magazines that reach your best prospects. The combination of direct mail, a solid website and trade magazine ads will add up to a well-rounded campaign.