Milk Paint Cracking- Just Live With It?

[Matt Lukes]

Avete omnes,

As the subject of this thread suggests, I'm having a bit of difficulty with my milk paint- it's cracking. I'm trying to paint a scutum that has a leather facing and while the back side that is just hide glue-soaked linen went just fine, the leather side is giving me nothing but grief. As the milk paint dries, a large number of hairline cracks form and I have as yet been unable to find any remedy. I sand down the whole thing with very light sandpaper to reduce any raised areas, and re-coat, but continue to get cracking at least minimally. Now the whole thing has a sort of rough texture up close that just bugs me :lol: That might be something that can be lived with for the background color, but it's starting to really suck with the painted decoration- yellow wings, etc.

Rich from LEGXX tells me they have the same problem at times, so I'm just wondering if it's just inherent to the medium or if anyone has found a solution to the problem.

I have found that it's not just the batch as it's happened with more than one color, and I'm not using any binders or other additives.

Any help would be appreciated.

Vale

Matt

[Peroni]

so I'm just wondering if it's just inherent to the medium

Maybe its the leather absorbing moisture from the air and expanding just enough to crack your paint.

The linen side has not done it because it hasn't the same inherent water absorption properties/capabilities as the leather?

Just a thought. :?

Regards,

[Cornelius Quintus]

Ave Matt,

in Medieval ages, the (leather covered) shield first was coated with a 'chalk-primer' (directly translated - I don't know the correct term for it in English).

This primer was a mix of champain-chalk (pure chalk), glue and water. (In German this glue is called 'Glutin-Leim').

Such a primer is still used by traditional painters today. It's advantage is beeing lissome/flexible due to the glue. So it won't crack compared to modern primers or unflexible paints.

I built a Norman kite shield last year, using the information from Jan Kohlmorgen's book "Der mittelalterliche Reiterschild" (= The Medieval Horseman Shield), featuring surviving originals and detailed reconstruction for re-enactment.

The author's receipe for this chalk primer for half a square meter is:

250 g chalk
25 g glue (bone-glue)
80 g zinc white (to make the grey chalk white - not necessary in any case)
water

perhaps that will work on your scutum.

Greetings from Germany

Heiko (Cornelius Quintus)

[Marcus Mummius]

Indeed that would be a good solution. I think the term you look for is 'Gesso' isn't it?

I plan to use this too when I paint a new scutum with milkpaint.

Valete,

[Matt Lukes]

Yes, that's a form of gesso alright Jef and it makes perfect sense considering that such a base is even used for artist's canvas. It should have occurred to me. The formulation is nice and simple- I wonder if one could simply add the glue to milk paint as a base coat? Since casein's acidity balances the lime's alkalinity so that the paint, when mixed, it might not damage the protein of the glue... I'll give it a try and see what happens. Otherwise I'll try the pure chalk method.

Thanks very much guys

Matt

[caiusbeerquitius]

For my first shield I had used milk paint I bought in the US (don´t know the name any more, something with "old fashioned" might be). I had the same problems you describe. With the paint from www.kreidezeit.de this problem does not occur if you follow strictly the instructions. A basic problem is, if you use leather and not rawhide, btw. Leather always is a soft ground, which will always make the hard cover of paint crack. The gesso described above and by Jan Kohlmorgen is quite usable, btw, I am using a similar material on the shield I am painting at the moment (Dura Amazonomachy). Hoever, a pure coat of glutin mixed with white milk paint is fine as well.

[Matt Lukes]

Mine's from the Old Fashioned Milk Paint Company too Christian- it's interesting to hear that the Kreidzeit version does not crack the same way. Given how basic the formulation of milk paint really is I wouldn't have expected much variation in its properties.

Well I will see shortly whether the paint+glue 'gesso' I just mixed-up works or not. I'm trying a 10:1 paint:glue ratio as Heiko's recipe suggests for the basic chalk version. I just really wish this had occurred to me at the beginning- it's going to be a real dicy chore to try and remove the paint down to the leather again without damaging the leather surface.

[Hibernicus]

And you can seal it all with beeswax. None of our parmas with milk paint show anysigns of cracking.

[caiusbeerquitius]

Better, cook the beeswax with pottassium. That makes punic wax.

[Marcus Mummius]

Is that punic wax completely transparant? How much potassium should one add (it is white isn't it?)?

And are you sure it's a good idea to use it to protect the paint on a shield against water? Did the romans use it? Read this:

Potassium was discovered in 1807 by Sir Humphrey Davy, who derived it from caustic potash (KOH). Potassium was the first metal that was isolated by electrolysis.

Potassium was not known in Roman times, and its names are not Classical Latin but rather neo-Latin.

Quote from: http://en.wikipedia.org/wiki/Potassium#Applications

Kind regards,

[Magnus]

That's why I use tremclad...hahahahahaha!

[Peroni]

Potassium was not known in Roman times, and its names are not Classical Latin but rather neo-Latin.

It may not have been a known quantity in Roman times, but it's properties were utilised from substances like wood ashes.

Birch bark ash was used in hair dye. Ash contains a certain ammount of potassium (potash) This is also why ashes are good for the garden. It can contain Nitrates which help plant growth.