Lichen recipe that seems to work.
Whilst experimenting with different applications for setting lichens onto a surface. I've built a limestone stone wall for my garden (now 5 years old) and have been dabbling with accelerated ageing ever since I had some success using recycled low fired clay bricks rebuilding a wall in the UK. I'm now in Australia, which is a pretty tough environment for lichens. I've tried various beer methods, the many yoghurt methods, the chicken dung method, only with relative success....until now.
This may seem strange and a witches brew, but humour me, Xanthoparmelia, Xanthoria and Caloplaca, love this.
For the base...
2 cups of hot (90 deg C) rainwater
1/2 tsp Agar powder. (growing medium)
1/2 tsp of Xanthan gum powder (complex sugars and a hardener for the Agar)
1/2 tsp of liquid seaweed fertiliser. (all sorts of 'starter' enzymes, proteins, sugars and beneficial nutrients in that)
Mix the powders and fertiliser in the hot water until it resembles wallpaper paste.
For the top coat...
1 cup of scrapings of your lichen plus any base adhesion.
1/2 cup of roof gutter sludge. Yes, that's right, that's probably where the Basidiomycete yeasts live. The Third Element.
Liquidise both together (with rainwater if needed) for about 5 seconds until you have a lumpy sludge, retaining some fragments of lichen.
Method.
Slap on a thick basecoat of the 'wallpaper paste' slurry with a thick brush to your substrate (preferably porous and pH neutral). Allow to soak in.
Then slap on the lichen sludge by stippling with the brush.
Cover and allow to dry until set.
Once dry and a crust has formed, heavily mist spray with rainwater every day it doesn't rain.
You should see some decent growth (a couple of millimeters!) within a year.
I was lucky enough to get a couple of barrowloads of lichen off an old corrugated cement roof, and upsized production with a cement mixer to cover this wall.
Results here here after 5 years. (right click and open image in new tab for closeup).
There's a combination of limestone, slate and serpentine in this wall. Lichen hates serpentine, possibly because it is has a high metal oxide content like iron,magnesium, zinc and copper, similar to basalt iron/magnesium based rock which is also not great for lichens.
For those interested, the plant background is Field Maple, Red Valerian, and Ground Ivy.