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Ensuring the coat of prussian blue on the granite is thick enough, but not too thick


Aug 31, 2007
It seems that a compromise/optimum is needed to obtain the right thickness of paint spread on the granite: not enough paint, and the blue will be very faint, hardly visible, too much paint, and you get "fake" high spots, in the extreme, even the lowest spots become blue,

I watched some videos where the pieces is rubbed (moved a few times) against the granite, I suppose this ensures that "enough" paint gets transferred.

I tried rubbing, and noticed that with too much rubbing, some paint is moved from high spots, to low spots, with too much rubbing, you end up with blue in valleys.

Are there any tricks to ensure that the coat of blue on the granite as thick enough, but not too thick ?

How much rubbing is too much ?

Am I using the right rubber roller to spread the paint (I ordered a roller on Scamazon, and the rubber is quite hard, too hard IMO) ?

Am I using the right paint ?

This is the paint I got:

If you just load the roller then try to roll out a square for printing it can be very hit and miss until you've done it a lot of times.

I roll out a square on another plate (or another part of the plate. Roll it out evenly both ways with my ink roller then use the roller (which should now have an even coating) to roll out the section of plate I'm printing from. The benefit is that you can do a quick test and see what your print looks like, and if it's thin, load the roller again and go over your patch or if it's thick, run the roller over a clean bit to take some of the blue off the roller then go over your square to remove a bit.
If you're moving blue into the low spots, it's too thick on the surface plate.
the development of "bull's eyes" could be described that way, as the blue is rubbed off the high spots and then forms a ring around them..... It depends on what was there to begin with as far as blue amount.

I think this issue is why I stick with a "dauber" instead of the roller. I just am not so good at getting the right coating thickness with the roller. Started with the dauber, and I guess I just got used to it.

The roller is a lot better if you have large areas to cover, though. I will need to get used to it if I do a surface plate. For now I have granite plates.
That Permatex bluing (it's not paint) in my opinion is the worst of all the blue as it smears. Go to a local art supply store and buy some Charbonnel Aqua engraving ink in a tube or small round tin can container. Get cardinal red, Prussian blue and some of the thinning agent that they also sell for the Charbonnel.
Use the red straight and dab it on with a finger in several places on your part and use a 1" foam paint roller to spread it all over the part, then wipe it off with a clean rag (cloth) so only the pours have red in them and the surface is dry to the touch.

Then the sqeeze some Prussian into a small container and dilute the blue 10 to one ink to thinking agent. Then dab that onto the granite plate ( I use Canode bluing and not the thinking agent) but it's hard to get in Canada I bet. Dab about 2" apart, then use a new foam roller to. Spread the ink so it is transparent (can see thru it and see the granite plate). Then use a hard rubber. Brayer (also buy at the art store) to get a consistent thickness and rub with a open hand the ink and part to feel for dirt. Then set the redded highlighter part on the plate and rub it to a count of 10, pivot (hinge) Lift it. Straight up and look at it. If there is a heavy smear use less ink. If it looks good rub the part on a clean area of the granite plate and that will shine up the highest high spots. Or buy the best tube bluing Dykem high spot bluing and no diluting is needed. But you will look like a smirf.


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Bluing ony pink granite plate and red or it maybe orange Charbonnel highlighter. I have the students draw diagonal lines on the part as a guide so they can scrape the checker board pattern. Spreading the ink is a science and if no one is showing you it's a pain. Put the Permatex in the garbage.


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Rich has a good point about blue application being a science. You’ll get the hang of it after a few hundred applications. You gotta trust your ink, develop a good relationship with it.
Today I mixed the Canode with Charbonnel and some denatured alcohol to thin out the old Canode. This a print of the actual part that was power scraped


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During my last scraping class one of my students who learned to scrape at Boeing had a really nice ink Brayer that the use at Boeing. It's better then the ones I buy from Amazon. It 2" diamond. With a heavy-duty handle.


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