rock formation

Discussion in 'FAQs' started by jimnrose, Sep 27, 2002.

  1. jimnrose

    jimnrose Member

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    At it again; needing help.
    I've formed the hills and mountaiins with hydrocal and plaster with pretty good satisfaction. The portals and waterfall areas came out good but I'm unable to develop the technique for rock and strata details. Could I add agrigate (crushed concrete or crusthed rock) to the plaster to get the rough finish?
    Any tips would be helpful...Thanks, Jim
    P.S. I have rock molds and will use them but my layout is too large for precasting all the rocks plus in lots of areas didn't allow sufficient depth for the molded rocks.
  2. shamus

    shamus Registered Member

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    Hi Jim,
    I carve my rockface with a small knife for all my strata detailing, I have posted a photo showing just some of it before painting begins.
    Shamus


    [​IMG]

    [​IMG]
  3. Jim de Bree

    Jim de Bree Member

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    Looks great as always Shamus. I have never been very good at rock carving. I use rock castings. I use the molds that have stratified rock and partially fill them with hydrocal to make a partial casting of only the part of the mold containing the stratification. The resulting casting generally pretty thin. I attach this to the existing scenery w/ fresh hydrocal paste (as shown in the Woodland Scenics Scenery videotape).
  4. jimnrose

    jimnrose Member

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    Hi Shamus & Jim,
    I know I'm repeating myself but Shamus you are unbelievable.
    I made a mistake when picking up the plaster and ended up with finishing grade rather than the scratch coat; that may be part of the problem; that coupled with uncertainty. I'll get the scratch grade and keep on pluging. Some day (hopefully) I'll wonder why I was making this task such a big deal. Your photo is very helpful, thanks again. Hope you are feeling better.
    Take care, Jim
  5. sumpter250

    sumpter250 multiscale modelbuilder

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    Jim,
    I wasn't too surprised to see Shamus' reply, handcarving his rock detail.
    I use the same technique. I work a small area at a time, laying on a coat of plaster, thick enough for the rock structure, and start working the plaster. Using a putty knife for the overall structure, while the plaster is soft. As the plaster gets harder, I go to smaller tools, and work in finer detail. When the plaster is hard, I use a dental pick for the smallest cracks. I wait until the plaster has dried for a couple of days, then stain with "dirty Diosol". I have also used a thin wash of laytex paint, at the club layout, to get away from the fumes.
    Pete
  6. shamus

    shamus Registered Member

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    Hi Jim,
    Now got the rocks painted and a few trees dotted around for effect, next chore is to grass and decorate it. (Icing on the cake)

    Shamus
    [​IMG]

    [​IMG]
  7. shamus

    shamus Registered Member

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    BTW, the plaster I use is called "Blue Hawk" undercoat plaster.
    Quite nice to work with and is not the soft stuff called (Finishing plaster)
    Shamus
    [​IMG]
  8. Xaniel

    Xaniel Member

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    Please,

    Give me some hints about puting the plaster on the layout and then to form that rough finish... (pics or thinks like that would be great...

    I want to start to add some scenery... :( :( :( :confused: :rolleyes: :D :D

    Thanks for your time...
  9. jimnrose

    jimnrose Member

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    Hi Shamus & Sumpter250,
    Let me start by saying I couldn't have gotten this far without your help and direction.
    I'm 40# into 'basecoat plaster' by USG and as you say Shamus, it's much easier to use than finished plaster and far better than hydrocal (although hydrocal is stronger), buuuuut I still don't get it. The standard mix rate (3:1) is too wet for sculpturing and I'll try what Sumpter250 recommends. I chickened out and used the molded rock approach plus some real rocks but most areas will require hand forming sooooo, I better keep at it. I'll try mixing a dryer batch and spray the matting surface plus have a few hand tools to form the details. Studying your photos, I can see the line details and assume they are drawn with a sharp edged instrument but the crevises and outcrops are something else. Are all the details done with one tool? (I believe you said a kitchen knife).
    Second question: Where do you get the time to sit at the keyboard and answer all these questions PLUS turn out breathtaking workmanship.
    Thanks AGAIN, Jim
  10. shamus

    shamus Registered Member

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    Hi Jim,
    If you are using the plaster I mentioned above, get a bowl and 1/4 fill it with cold water - now add the paster until it is just like thick porridge, (stiring all the time)now it's ready for use.

    Shamus
    [​IMG]
  11. jimnrose

    jimnrose Member

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    Shamus,
    I mixed the plaster as you suggested and it sure makes the task a lot easier. I made a print of your photo attempting to copy the technique. 'Forget it' as the kids would say. Luckily I had a cup or two of cut blue stone 9.5 TO 1 cm) and stuck them into the plaster. At my skill level, this is much easier combined with using mold rocks. I just hand sculptured a granite cliff (phot ofrom Dave Frary) and it came out pretty good. It was a lot easier to simulate but I'll try your pattern on small sections between the molded rocks and hopefully will develop the skill to handle a large section. Take care & thanks AGAIN. Jim
  12. sumpter250

    sumpter250 multiscale modelbuilder

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    Jim,
    Two comments:
    Don't try too large a section at a time, the plaster will harden before all the detail can be worked in. I usually do no larger than 10' X 10" area. It helps to wet the area before applying the plaster, and, as Shamus suggested, mix the plaster to a porridge consistency.(it can "droop" a little when applied, but shouldn't run)
    Adding real rock to the "handcarved" area could lead to difficulties getting the colors to blend. If you have a piece of rock that's just too good looking to pass up, it's better to make a mold, and cast it in the same plaster. It will be easier to color.
    Pete
  13. jimnrose

    jimnrose Member

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    Pete,
    Thanks for your recommendations. I've been pretty successful hand carving a granite section (12" x 10"). [Small sections for little skills]. Also went back after the plaster was semi-hard and scrapped off the tell tale tool marks. On the addition of real rocks I was planning to use finish plaster to cover the rock surface thereby enabling me to treat all surfaces the same. Does that make sense? I realize that I need to have a pretty thin plaster coating to avoid loosing the rock details.
    Take care, Jim