As the title states, I have a question regarding homemade mud effects.
Does it matter if I have something like fertilizer in the dirt I will be using? I don’t really have much of a choice in the dirt I use, as it is currently 30 below and covered in a half a foot of snow outside.
My only two ideas currently are to roll with the larger pieces, or go and take each piece out by hand.
If you can see the pieces of fertilizer and are contemplating removing them, there’s a problem. Fertilizer contains nitrates, nitrates are oxidizers, oxidizers chemically oxidize things, like paint. See where this is going? If we are talking about a few parts per million from last summer’s lawn care, don’t worry about it. If someone spilled the bag on the dirt you are about to use, look elsewhere for your diorama dirt, like in the crawl space under the house.
As an alternative you could always try an easy way to create your own mud- using thinned enamel paint or an enamel based weathering product. Get some powdered wall filler from the DIY store and mix it up. For thick mud use more powder- and the reverse for a thinner mix.
I use powdered silica from a pottery supply store as a paint mix-in. Chemically inert so it doesn’t mess with your paint. Don’t be tempted to use Baking Soda however, (despite other’s endorsements in favor), Sodium Bicarbonate is not chemically stable, it will lose its hydrogen ion within 2 years and deteriorate into Sodium Carbonate, leaving your paint a goopy mess. Been there, done that.
I use that too, Golden Acrylics brand, if I want soupy mud. If I want chunky-style, I throw in the silica powder and maybe some static grass as well. Works fine for on-vehicle mud, a bit pricey for overall diorama work, unless it’s just a small area. Cell-u-Clay, et al., can also be used, alone or with the other mix-ins.
For 1:35 scale, like Karl I use wall-filler as a base mixed with sand and/or fine railway ballast. That makes a grey-ish textured sludge so I add some earthy powder-paint shades plus black to get variations of tone, because monochrome mud doesn’t look much good. If it needs highlighting I dry-brush light shades of pastel dust when it’s all in situ & dry.
After preheating the dirt as digger303 suggested, mix in a hefty portion of white glue into your dirt/mud slurry and you 'll be good to go. I have a couple of old dioramas from 1976-77 and they look exactly the same as when they were made.
Thank you everyone for all the help. I think I’ll opt to try the technique with preheating, but I will also go out and buy some wall filler so I don’t have to worry about not being able to find non-permafrosted ground.
PVA glue. A touch of acrylic paint of the colour of choice. Mix in some plaster of Paris. The plaster give some texture. The colour gives a good base colour. The PVA will stick and hold on. For whatever reason this combination takes sometime to set so plenty of time to ‘play’.