Re: Stock Paint:Gum Solutions?
Loris, I have been using Mowiol on/off the last couple weeks. The 8-88 variety recommended by Mr Jeanlis was sold out at Kremer's so I used 4-88 (310grs per litre of water). I don't know if I will be using it much in the future, it reacts differently than gum of course. It seems to be slower than gum : MY exposure times for gum are between 2 and 3:30 mins, Mowiol needs 7 to 10 mins exposure. It seems to dry slower and requires some heat to loose it's tackiness. What I do like is the fact that a mixture of Mowiol, paint and pot dichromat does not seem to get bad, even after 2 weeks. Best, Guido 2008/10/24 Loris Medici <mail@loris.medici.name>: > 24 Ekim 2008, Cuma, 9:41 am tarihinde, Alberto Novo yazmış: >> ...Also very confusing is parts/parts, because the units of >> such parts are not declared. Is it weight/weight, or volume/volume? >> In the first case, 1+3 leads to 25% w/w, and 1+2 leads to 33% w/w... > > I always assumed that 1+2 is w/w since gum can be in various forms; > powder, tears and lumps, therefore the only logical conclusion is that > it's expressed in w/w (or w/v, since density of water is 1 g/ml, therefore > weight and volume are interchangeable - keeping the scale proportional). I > mix it 100g gum into 200ml (200g) water. The consistency is very good that > way, when using 1+1 coating solution (v/v, paint/gum+dichromate solutions) > -> in watercolor, that corresponds to fluid concentration (1:6), according > to paint amnt. in the coating solution, or creamy concentration according > to gum amnt... I guess both are fine for getting good results(!?), the > choice depending on practitioner's personal preference (and not to any > kind of technical limitation). > > Of course, still, there's the problem of gum not being a defined compound > (it can change depending on source and year of harvest). Therefore I'm > interested in synthetic alternative such as PVA. I haven't find a good > source of suitable PVA, plus, I'm not completely sure which kind of PVA is > most suitable for our purposes. As soon as I figure these out (source and > type), I'll leave gum aside and use PVA as the colloid. (My current > understanding is that something like 85% hydrolized, with a molecular mass > around 10 - 12.000 should do well... Any thoughts?) > > Regards, > Loris. > >
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