Until recently I was unsure if Denby produced insulators but thanks to a couple of contributers, I can confirm they did and that the brown stoneware Varley No.8 was one of them.
It all started with an email from a chap in Derbyshire....
Last wednesday (March 21st), while taking my dog for a walk, we passed a large plot of land at the back of a cottage, (as we have done for many years), except, just recently, the owner has cleared the land of all the thickly overgrown bracken, brambles, and blackberry bushes from the site. All that is left in one corner is a stone grinding wheel supported on 2 thick stone supports. I spoke to the owner, who does not know its purpose, but he did show me a host of broken bits of pottery that is scattered all over the land, these are finished, glazed pottery items. He invited me onto the land to inspect it and said to look around, there are hundreds of pieces, and just scratching the surface produced more pieces of stoneware plates, all glazed - and I pulled out of the ground an obect that was complete, a stoneware brown, one piece item, which when cleaned of the soil, shows engraved words "8 VARLEY'S PATENT".
We had no idea what it was, but the gentleman said take it along with anything else you pick up. I was so keen to find out what I had unearthed, i went on the internet the next night and found your website, and have found it to be a saltglazed stoneware insulator, of one piece construction. It stands 4 1/4" tall, weighs 1 lb 7 oz, and the groove for the wire is approx 10mm wide. It appears to have been unused, for the hollow inside is mint, and the screw thread inside is also in mint condition. The top of the insulator towards one side has a chip to it, and there is 1 vertical hairline crack, and a hairline crack where the groove is.
I have done some further research, and it appears that the land where all these pottery items are, could have been the finished goods warehouse of the 19th century Belper Pottery, which was purchased by William Bourne in 1800 (he was the father of Joseph Bourne, whom William set up in business in the nearby village of Denby, Derbyshire, after having discovered a rich seam of clay in 1806 while the turnpike from Derby to Alfreton was being built). The Denby factory flourished into the now world famous Denby Pottery. William Bourne continued to manufacture pottery at Belper, with pottery being made there possibly through to the end of the nineteenth century, (no found exact dates yet)
From the description, it sounds like an outer of a Double Varley, i.e the inner shed has yet to be cemented in. Note the finger marks left by the last person to handle the insulator prior to it being fired and glazed. I have seen this on other insulators, in particular, stoneware standard line insulators, examples of which I have recently found in Ireland.
This email aroused my interest in Denby and quick trawl through the search engines revealed. Philip Mernick's webpage devoted to Denby jugs, obviously a man who knows a bit about Denby.
After relaying the previous email to Phil he kindly replied with the following information....
I checked out the standard book on Denby, Denby Pottery 1809-1997 by Irene & Gordon Hopwood and they mention insulators several times as being an important product for Denby. Apparently one of their employees invented a lathe for making them in 1883 and there is a mention of an 1880 advertisement in The Pottery Gazette that focussed on telegraph insulators and battery cells. They were still making insulators for The Post Office during World War 2. There is an illustration of a catalogue page (1880) that includes an insulator (Varley type from your web pictures). Bourne's Belper pottery closed in 1838 which sounds a bit early for insulators.
and a further reply...
I have just found the following references to Denby production of insulators in Ceramic Art of Great Britain by Llewellynn Jewitt. 1878 (first edition). "Much thought and care as well as considerable expense has been expended during the last twenty years to perfect the manufacture of telegraph insulators, and the very large business transactions in this department proves that the enterprise of the firm has not been fruitless.
Messrs. Bourne and Son have for many years possessed the exclusive right to manufacture Mr. Varley's Patent Double V. Insulators, and since the transfer of the telegraphs to the Government, the firm has executed immense quantities for that department of the public service."
1883 (second edition). As above, plus "The firm also supplies large quantities of other patented insulators to the great English railway companies and private electrical engineering firms, and large orders have been recently received from the Canadian railway companies, these insulators being found much more efficient than the glass ones generally used on the North American Continent. The National Telephone Company has recently adopted insulators produced by this firm."
My Current Thinkings
Denby were obviously making insulators in the mid 1850s, confirmed by the phrase, Much thought and care as well as considerable expense has been expended during the last twenty years to perfect the manufacture of telegraph insulators as quoted in the 1878 book extract.
They continued to make insulators for the Post Office (G.P.O) during World War II and possibly / probably are the makers of the brown Stoneware Terminators and Standard Line Insulators which are impressed G.P.O. on the top face and can still be seen on poles today.
Most, brown Stoneware, GPO marked insulators usually have an extended inner shed with a pale brown, unglazed bottom suggesting the same type of clay as in Varleys Patent impressed insulators without a manufacturers stamp.
Gene Kingsley forwarded on some extra information as follows
I have just read your article on Denby insulators and it reminded me that a fellow collector told me that the white glazed stoneware small and large terminators with blue inked GPO on top were made by denby and the clay looks exactly the same as unglazed denby.