Ran outa metal marking stuff..using straight plaster of paris

[Rodne Gold]

We ran out of cerdec and can't get any over here , None of the local laser guys here in South Africa are carrying cerdec anymore..they recon its too expensive..
So I tried using straight plaster of paris and it works a charm...using it on Stainless and titanium. I tried my scotchpad torture test (Vigorous high pressure rubbing for at least a minute) on the resultant mark (and the same on a cerdeced mark) and it held up as well as the Cerdec. We just have to run a little slower for a good mark..the mark is also not quite as black but nothing to be that concerned about as we are doing industrial type work. Only bug bear is that the stuff sets so when mixing , we don't have a long time to apply , washing off is no problem.

[Dan Hintz]

Yeah, if it wasn't for the several large containers of Cermark I picked up in an estate sale, I would have switched over to PoP when we fist discussed it years back.

[Mike Null]

Dan

Sounds like a great opportunity to list something on the classified forum. As far as I know that stuff has unlimited shelf life.

[Dan Hintz]

I have a growing list of things that need to go in an ad... 2HP Leeson motor, Sorby sharpening jigs, etc. But that requires effort on my part ;)

[Joe Hillmann]

Rodne,

How exactly do you mix and apply the plaster of Paris to the parts?

[Rodne Gold]

Thin it with water to about the same consistency as Cerdec and apply it thinly with a brush.

[Isaac Clarke]

Do you wait for it to dry or fire away once its on the part.

Thanks, Isaac

[Rodne Gold]

waited for it to dry , the thin layer washes off easily.

[Matt Turner (physics)]

Thin it with water to about the same consistency as Cerdec and apply it thinly with a brush.

For those of us who have never used Cerdec (or any other marking compound), can you give another example of the consistency? Thanks!

[Rodne Gold]

A Thin watery paste with a viscosity of between milk and cream... you want a thin even layer when it dries.. the thinner the better, but not so thin that metal shows thru.

[Ross Moshinsky]

I think threads like these are informative but I think there is one real question that remains.

Are you buying Cermark/Cerdec or are you sticking with Plaster of Paris?

[Richard Rumancik]

I was wondering the same thing as Ross. In the past there were threads where various members showed excitement about PoP as a substitute but then the enthusiasm always tended to die down. Maybe because it really doesn't work as well? Rodne, you have power to spare but those of us with lower wattage machines might not be able to afford a slower production rate.

I did try "plaster of paris" a few years ago and it "sorta" worked but not ready for prime time (for my applications) and I did not really have the time to experiment and refine it. What I did learn is that "plaster of paris" can mean different things to different manufacturers. For example DAP sells a box labeled Plaster of Paris which contains calcium sulfate, calcium carbonate, and crystaline silica. They do not indicate proportions. I suspect that the silica is just a filler and might not even be a benefit for this application. Rodne, out of curiosity, does your PoP show what is actually in it? I suspect that the success some individuals got may be somewhat dependent on the recipe for PoP that was being used.

[Michael Kowalczyk]

So can PoP be sprayed with an air brush? and is it UV stable?

[Rodne Gold]

Well , the issue is that we *CANNOT GET* cerdec/whatevermetalemarkingpaste here..unless I import directly... so what do I do?
I wouldn't have tried anything else if I could have got what I always use..in bulk it might be pricey , but cost per item for cerdec isn't high in relation to selling price..and we know it works....

I will stick to POP until one of my suppliers gets stock and maybe stick with POP even if they do...

Our 2lb box is from a candle making supply co , just has a label saying Plaster of Paris. Cost about $2..Obviously decanted from a bulk lot.

I suppose you can spray with an airbrush , clean well after..tho a simple brush works for me. I have no idea of whether the mark is UV stable , its impossible to remove , so I cant see it "fading"

We don't have to slow the lasers down by huge amounts , and I'm using a low power 30w laser to do this , perhaps a 15% speed reduction..slightly slower is no problem for me , its either that or lose the job altogether

The idea to try POP *WAS* from previous discussions here, thanks to whomsoever "discovered" it , saved my bacon.

[Dan Hintz]

For those wishing to use an airbrush... use a large nozzle, screen mesh the PoP beforehand, or both. DAMHIKT.