Source for pitch

[dark star]

Does anyone know a good source for pitch for making a pitch lap? The only one I know is Galvoptics, but they are not cheap. 'Best pitch' is £12.10 for 450g and 'special pitch' is £16.74 for 450g. I bought some best pitch from them. It was fine, but rather hard. I ended up mixing in 3 teaspoons of linseed oil to make it softer. If I buy from them again I will get 'special pitch' just to see what the difference is. Next time I will buy rather a lot as I have got the mirror making bug! I have nearly finished a 6 inch mirror and have just started grinding a 14 inch, but I think I may well do another one after that.  

David

[Glasspusher]

David,

Getting hold of any pitch in the UK is difficult. Some people are  buying from the US, you could try here...https://www.willbell.com/ATMSupplies/ATM_Supplies.htm.

It will be interesting to see if anyone comes up with a UK source other than Galvoptics! Good luck with the 14 inch.

John

[Astrobits]

You could try VCSM:

http://www.scientificmirrors.co.uk/index.html

I am planning to use pitch ( bitumen ) from a roofing supplier for my next mirror:

http://www.ashbrookroofing.co.uk/easymelt-95-25-grade-bonding-bitumen-blocks-bitumen-kegs-10kg

Will have to see how it goes.

Nigel

[dark star]

I did contact Vacuum Coatings not so long ago, and they still have no pitch. I bought my 6 inch mirror and grinding grit from them, they are very helpful. Pity they have no pitch as they are not far from where I live.

Good look with the Bitumen, if it works it will certainly be a lot cheaper!

David

[dark star]

I am probably going to buy a cube beam splitter and biconvex lens from Galvoptics, as I am in the process of trying to construct a bath interferometer for testing mirrors, so I will probably get the pitch from them as well. I would be surprised if buying from America would be cheaper for pitch, although I should work out how much it would cost, just out of interest. I need to ring Galvoptics to find out the price of the beam splitter and lens, as I could not find a price on their website.

I will post about the bath interferometer when (if!) I get it working.

David

[Astrobits]

I have used roofing pitch successfully in the past but it was very hard and needed plenty of Turpentine to make it useable. As pitch can come from various sources every supply could perform differently.

Nigel