Topic: When is a crack not a crack

[lyndhurst44]

The piece is a piece of Art Deco green vaseline glass by either Walther or Sowerby, I believe it is known as a Greta vase. Towards the base there is a crack or what assumes to be a crack. The reason I say this is that the mark only appears to be on the outside of the vase and can be, albeit, lightly felt, the same area on the inside is completely smooth. Would this be what I have heard as being a straw line?, created when the item was made. The mark runs for about 2.5" over a clear area and into a frosted part.

Thanks,
Bryn (not Brian)

[Frank]

Looks like a mould line.

[Anne]

Bryn, it doesn't look like a crack from what I can see.

Frank, what's the difference between a mould line and a straw mark please?

[Frank]

Glen gave a good account of the straw mark recently, it is caused by a cooler tool contacting hot metal as it is cut off at the mould. Whereas a mould line occurs where the different parts of the mould came together, the more a mould is used the more it wears and differences in wear rate mean that the mould loses exavt registration (If it was well enough made to cast mark free to start with, of course.)

[Anne]

Frank, what's the difference between a mould line and a straw mark please?

That's what I thought you were meaning, thanks. The mark on Bryn's vase is a horizontal one across the pattern which wouldn't appear to be a result of the mould would it? So that would make it more likely to be a straw mark then?

[Frank]

Impossible for it to be a straw mark in that position. Definitely a mould mark, probably made on a bottle press machine.

[Lustrousstone]

I too would go with the not a crack option. Cracks look more kind of silvery when you turn them so the light catches them. Just a manufacturing mark

[Adam]

I've come to this post rather late in the day.  Are we talking about the horizontal, dark coloured line very close to the base or to the whitish, thin line further up, also horizontal?  I can't work out what the bottom one is from the picture, but the top one looks like a crack in the iron mould.  Sorry, Frank, but I can't see either of these as a mould mark, in the sense of a joint or section mark - or have I misunderstood you?

Adam D.

[Frank]

A crack in the mould does resolve the puzzle of position which I had quietly ignored until now. I had some fanciful ideas as to how it could be a joint or section mark but as I could not be certain, left them out. So thank you for coming in with that Adam. I think the dark lines is an unrelated reflection.

[lyndhurst44]

Yes the dark line is a just a reflection caused by the flash, the upper line is the mark in question.

Bryn (not Brian)