Stuarts Micrometer Blue - does it 'go off'?

small.planes · Mar 12, 2021

Hi all,
I have a fairly old (15 or so years) tin of Stuarts Micrometer blue - its oil based prussian blue as far as I know and is the most common in the UK I think.

I think it has got to 'stiff' - it doesn't seem to spread very well.
I assume it doesn't 'go off'?
I think all I need to do is add a little oil? I have a selection of machine tool oils - from spindle to thick and gooey.
Right now it will hold a peak, sort of like meringue egg whites, but I think it should be more like soft toothpaste.
I don't know what consistency it should be?

Dave

eKretz · Mar 12, 2021

I've only used the Dykem stuff, but it's thick enough to hold a peak brand new. Generally I'd describe its consistency like a very thin grease. Don't know if that stuff you've got is different.

Mark Rand · Mar 12, 2021

The tins do tend to dry out over the years. A few drops of the lightest oil you can find and a LOT of careful kneading/stirring (while wearing rubber gloves/full isolation suit) will get it back to usable consistency. The tubes last better, if not trodden on, but the oil can separate from the pigment if undisturbed for some years. That isn't usually a problem though, just means that the first drop from a long unused tube can be weak and need throwing away.

Lurk · Mar 21, 2021

I was givena tin - battered as it was and to be honest was going to chuck it away as i had a couple of new tubes - however, I found it worked really well when applied by a rubber (cotton cloth wound up tight) - it spread to virtually nothing. As mark says, you can add a spot of oil and rework it - but its time consuming. Ive also added a touch of white spirit - quicker to work in and it evaporates - but handy if you want a 'haze' when hunting for odd high spots.

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Stuarts Micrometer Blue - does it 'go off'?

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