foil spacers

I just received a new set of manufacturer's foil spacers for a refractor lens. While the backs of the spacers are sticky, there seems to be nothing on the exposed top surfaces. It seems to me that there they need some tacky substance applied to hold lenses in place. Does anyone know what is used for this purpose? I suppose I could just hold lens elements together via pressure from the retaining ring alone. However, I'd rather not rely on retaining ring alone.

Thanks

I have seen very few refractor lenses with
adhesive on both sides of the spacers.
There could be some concern about diffrerent
rates of expansion / contraction for the two
elements. When scope goes from warm indoors to
cold outdoors, the front element contracts much
faster than rear element. Maybe if they were
stuck together something bad could happen?
I have only seen maybe one Chinese 6"
refractor where elements were "glued" together
at the spacers, out of maybe 3 dozen refractors.

The retaining ring will give plenty of force to
keep elements together. I agree maybe it is nice
to prevent rotation of the elements, but perhaps
there is better way to do it.

Bruce,

I don't recall ever seeing both sides of a foil spacer with adhesive. I can imagine if it was done there might be a time when you would have to pry the elements apart.

Once a lens is assembled, a little cellophane tape spaced around the edge will go a long way to reduce movement of the glasses. These don't need to cover the entire edge. Three strips about 1" long are adequate for a 4-6" lens. The lens can then be handled to get it securely into the cell.

dan

Bruce,
Install one spacer with sticky side down, two with sticky side up. And hooray for correctly fitting cells, they aren't made for you, they are made for "them".
Ron