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plaster crown

donpapenburg | Posted in General Discussion on December 22, 2004 07:46am

I would like to try making plaster crown mold . Does anyone have a link or know of a book that explains this.  I have some idea but I know I don’t know it all.

Any tricks and tecniques would be helpful.

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  1. donpapenburg | Dec 23, 2004 04:50am | #1

    boink or bump or both

  2. FastEddie1 | Dec 23, 2004 05:29am | #2

    I saw it done once on an old This Old House show.  They made a template of stiff aluminum, then drug it along some plaster slopped on the wall, and voila they had crown moulding.  But I think it took some practice and skill.  Looked very interesting.  I think one of the advanteges was that you could use the technique to do curved crown over a window.

     

    I'm sorry, I thought you wanted it done the right way.

  3. User avater
    JDRHI | Dec 23, 2004 06:37am | #3

    I`ve done it on a few occasions when attempting to match existing.

    Aint all that hard....just time consuming and demanding of patience.

    Depending upon how ornate you plan on getting, will be a deciding factor in how much patience will be required. The few times I`ve done it, the molds were rather simple.

    First off, decide on a size (ht.) and a profile. If I recall correctly, six feet is pretty much the maximum length you want to make each piece. You`ll need to make up some troughs....mind you, I don`t know thats what they`re called, but thats what I`m callin` them. Plywood and some two bys. A pictures worth a thousand words....so I`m attatching a sketch.

    Cut a semi flexible taping knife to width, and profile you wish to acheive.

    Start mixing up your plaster. Don`t attempt to do it in one shot....its gonna take several. Mix enough to work with and fill the troughs length. Again......yer not trying this in one pass.....fill it an inch deep or so across the length of the trough. Now start dragging your knife through it. Slowly and steadily. As it starts to set....let up.

    Allow it to set and move on to the next length. After all your lengths have set....start over. Add another layer of plaster and start draggin`. Continue the process until you`ve acheived the completed profile.

    Best of luck to ya....posty some pics when you get the chance.

    J. D. Reynolds

    Home Improvements

    "DO IT RIGHT, DO IT ONCE"

    1. ponytl | Dec 23, 2004 08:07am | #4

      I've always cast it in place (both times)... yes over head ect...   for a wide crown I first  used a plywood cant in place... covered it with metal lath cut my metal template added a wood handle to it...  attached a 1x2 to the wall to use as a guide with a helper slop'n the plaster onto the metal lath i'd drag or push the template forward... not worry'n to much on the first pass how much we got up... the stuff we used set up pretty quick but wasn't much to "drag" a 20 ft wall... the second pass you'd start to tell it was crown... the third pass would usually fill remaining voids... corners took a little time with any tool we could press into use...  but for not knowing what we were doing except a few pages from a book it looked as good as any i'd seen...

      kinda fun to do... messy and wish i'd done it on my curved windows at home... I'll do it again...

      pony

      1. donpapenburg | Dec 24, 2004 05:01pm | #10

         When you were done how thick was your plaster over the cant strip?

        1. ponytl | Dec 25, 2004 04:46am | #23

          i was what  make'n amounted to about a 12" crown... seems the plywood cant strip & wire lath fell about  a 1/2 inch below the thinest part...  I do know i mixed up the plaster using some formula i found in an old book... it was a plaster lime mix... it was thick but very smooth and easy to work with to a point then it seemed to take a "set" and you wanted to leave it alone after that... if / when i do it again i might try using some poly fiber in it ( the stuff u put in fiber concrete)  the template i made i used an old piece of alum about an 1/8 inch thick... the shape wasn't too trick i used a scrap of old crown and traced it onto it 2x (it was 6" crown)  i cut the alum with a jig saw and used a file to touch it up... keep'n the templace at a dead 90 to the wall was the only trick... might be able to screw a guide to the template for better control... and a dead flat wall would sure help...

          merry christmas all... if thats still "pc" 

          1. JerBear | Dec 25, 2004 06:05am | #24

            That's how it's done.  It's just important the wall and cieling be true.

          2. donpapenburg | Dec 25, 2004 07:08pm | #25

            My wall and ceiling are close  to straight .  I had planed on  scimm coating the ceiling, then running the crown and  scimm coating the walls last . Figureing that I could cover the holes for the track and do the wall in one shot. 

          3. FastEddie1 | Dec 25, 2004 09:32pm | #26

            I am trying really, really hard to not make comments about other posters spellings, but you got my curiosity on this one.  You spelled it the same way twice so it's not a typo.  What is "scimm"?

             I'm sorry, I thought you wanted it done the right way.

          4. UncleDunc | Dec 25, 2004 09:53pm | #27

            Skim.

          5. donpapenburg | Dec 26, 2004 07:16am | #29

            I knew that it looked wrong but for some reason I did not check . But did it sound like skim when you read it?  Any way it is just two to three coats of very thin layers of topping compound . USG darker blue lid.

          6. FastEddie1 | Dec 26, 2004 09:38am | #31

            It looked like one of them ferrin words ... like from the frozen north they calls Canuckland.

             I'm sorry, I thought you wanted it done the right way.

    2. dinothecarpenter | Dec 23, 2004 05:09pm | #6

      Two more things to make it ezier.

      Extend the upper portion of your tape knife with a piece of wood or metal in order for your tape knife to ride in top of the form giving you the depth control.

      Or for 4' crown use a 6" tape knife 

      use wax on the form for EZier removal of molding.

      And fiberglass tape as a reinforcement. (not flat)

      YCF.Dino

       

       

      1. User avater
        Sphere | Dec 23, 2004 07:11pm | #7

        got google?There is THE foremost expert in greenlane, Pa on the subject..I think he wrote a book, but not sure..I'd jump on that avenue first.Might be an Italin guy? I ferget, but lived there and sorta knew him..'bout 20 yrs ago.If ya need help googlin..lemme know. 

        Spheramid Enterprises Architectural Woodworks

        Repairs, Remodeling, Restorations. 

         

         

        1. donpapenburg | Dec 24, 2004 04:52pm | #8

          Thanks to all that replied !!!  

          I had planned on running the crown in place as this is a curved wall  with a pitched ceiling ( about 3/12 I don't think it qualifies as a cathederal ceiling)  .

           What type of plaster did you guys use?

          We thought that we would try plaster of paris as it is sold in the stores around here.

          After you have a length made in a tray ,how do you faten it to the wall/ceiling ? Do you butter the back/top of the molding or the wall /ceiling or both?

           Sphere , who is the guy that wrote the book and what is the name of the book?   See if you can dig that up if you got all your snow shoveled. 

          1. User avater
            Sphere | Dec 24, 2004 06:18pm | #12

            nuthin to shovel here, just chipping off all the ice.Still can't open my van doors..aarrghh.Um, I tried to locate the info. but had no luck. He may be dead for all I know. Sorry..I swear he was in the area and fairly well known as the best..was on TOH at time or another, or one of those shows. 

            Spheramid Enterprises Architectural Woodworks

            Repairs, Remodeling, Restorations. 

             

             

          2. UncleDunc | Dec 24, 2004 08:05pm | #15

            >> Still can't open my van doors.Have you tried hot water?

          3. FastEddie1 | Dec 24, 2004 08:47pm | #16

            Have you tried hot water?  How is he supposed to get the van into the shower?I'm sorry, I thought you wanted it done the right way.

          4. FastEddie1 | Dec 24, 2004 06:28pm | #13

            Rather than plain plaster, you might try some setting-type sheetrock joint compound.  It's the stuff that comes as a dry powder and you mix as needed.  If you're feeling gutsy, you can get a batch that sets in 10 minutes.  Slower times are also readily available.

            With regard to your ceiling slope ... I think that generally, any celiing that slopes is called a cathederal ceiling, as opposed to a flat one.I'm sorry, I thought you wanted it done the right way.

          5. IanDG | Dec 24, 2004 08:58pm | #17

            In '54, I spent a summer vacation helping our plasterer foreman run sections of crown to match the existing in an 1830s house.

            To copy the existing profile [I realise you don't need to do this, but someone might] he oiled a section of the crown with linseed oil and slapped on a plaster patch, reinforced with burlap.

            When that set, he prised it off and sawed it in half to show the section. He cut a piece of zinc sheet to the section and sandwiched it between two pieces of board to stiffen it. The bottom edges of the board were notched to ride on a 1" x 2" that was nailed horizontally to the wall just below the position of the crown to act like a rail for the boards/profile [called a 'Horse', BTW] to run on and the top of the horse was cut so that it would run along the ceiling.

            He started by soaking burlap in wet plaster and slapping it up into the angle of the ceiling/wall to roughly fill it out to within 1/2" of the finished crown and that was allowed to dry.

            The plaster for the finish was 'Mountford' plaster, which is a very fine grain, quick-setting plaster much like Plaster of Paris. Wet plaster was applied to the burlap/plaster base and the horse was pushed backwards and forwards along its rail to scrape the profile [taking care to keep it tight to wall and ceiling] -- more plaster being added to fill voids. The corners were formed by hand, using a variety of 'spoons' which looked like little trowels and knives.

            IanDG

          6. dinothecarpenter | Dec 24, 2004 11:26pm | #18

            Imagine a 12"' wide and 4""to 1'' thick molding around a Gothic  Door 10" feet high.

            We build and install 2 doors for  this cathedral in Elizabeth NJ a long time ago.The Job was done but we can't get the final payment ($35.000.00)because the plaster molding was'nt done. 

            2 guys from NY (artist's) was commission to duplicate the plaster profile around the door opening. ($10.000.00 budget) and 2 month's later... I can't get pay because they just can't do it. The funny thing here was that I ask them the first day if I can help them. They look at me like...Don't you know who we're? The best artists from NY. Get lost you.. carpenter.

            Few days before the -(Grand opening) (from a Major fire damage) I was given the ok by the priest and the Lloyd's ins. representative to get it done.

            4 hours to build the forms.(plywood) 2 hours to make 8-3 feet sections of molding. 2 hours to install  and 2 more to touch-up.   The whole trick was to make the moldings in sections... at the floor. I don't even have the time to build tables. 

            But the real problem was the walls. This guys was trying to build the plaster profile in place on walls that another plasterer  just rebuild wrong. The first thing was to Fix  the walls. That take  a whole day.

            So, from this We should learn to "scout"  the space before we attempt any work.

          7. IanDG | Dec 24, 2004 11:59pm | #19

            Seems to me it would call for precast sections with the corners built in-situ. I wouldn't try to run it.

            Didn't it have any sort of moulding? -- dentil or such?

            IanDG

          8. dinothecarpenter | Dec 25, 2004 12:26am | #20

            It was the opening of a doorway. Heavy and part of the wall. No detail molding.

            The door was two feet back from the wall. And the opening 2 feet larger than the door. So what we have to deal with was 2 elliptical sections meeting in the top.The detail was in the corner all the way around the  opening.

            It sounds difficult, but it was very Ez after we replaster the whole opening using a template from another opening. I think with plaster is all about templates.

            YCf Dino 

      2. donpapenburg | Dec 24, 2004 04:57pm | #9

        What do you mean by fiberglass tape (not flat) ?

         Do you mean push the tape into the contuor and run more mud or is there another type of tape?

        1. dinothecarpenter | Dec 24, 2004 05:59pm | #11

          I don't know how to say it.  Use the f/tape as a wire mesh. Make it like 3d?

          Ok Let me try this way. For 12" of molding use 3-4 feet of f/tape.

          If you're building the molding in place.First you build the form-guide left and right and at the bottom-back of  the molding screw some screws to act like a key.or screw wire mesh.

          The form is 90% of the work.

          YCF Dino

    3. donpapenburg | Jan 02, 2005 07:53am | #32

      So how did you install the strips that you cast  in a mold or run in a tray? Most of the advice that I got for running in place suggest that I have a secure connection to the wall/ceiling.

      1. User avater
        JDRHI | Jan 02, 2005 11:24pm | #33

        As I mentioned, I`ve only done repairs....minor for the most part.

        I predrilled and nailed for the most part. The heavier peices were drilled and screwed in place. You just need to be sure where you have nailing. Filling the holes with plaster and sanding makes it all look like it was always there.J. D. Reynolds

        Home Improvements

        "DO IT RIGHT, DO IT ONCE"

        1. donpapenburg | Jan 03, 2005 05:21pm | #34

          Thanks , I think that someone wrote that they set it in a thin bed of wet plaster.  Then others said that if I was running it in place to make sure I had it escured to the wall/ceiling . Got me to thinking that the plaster would not hold the pre formed .

  4. HeavyDuty | Dec 23, 2004 09:39am | #5

    There are two ways to fabricate plaster crowns, you can cast it in place or like Jay said cast it in a trough and put it up in pieces. They are usually done in 6' length.

    For more ornate mouldings e.g. dentil, reed and eggs and darts, you have to cast it in a flexable mould. Then there is where you would use special casting plaster and muslin reinforcement.

  5. bigfootnampa | Dec 24, 2004 07:04pm | #14
    My experience with such jobs has all been repairs.  I did have to do a cove molding replacement that was full room width though.  I roughed it in by eye with a piece of metal lath curved in for backer and refined it with a wooden template and then finished by sanding and with some small trowels for touch up (especially in the corners).  I used Durabond joint compound for the face and some Gypsolite as a base.  That makes a good durable installation but I'd probably use a regular finish lime and plaster mix for a face now, because the creamy mixture is easier to form (the Durabond has a fair amount of glue in it and is a little stickier).



    Edited 12/24/2004 11:12 am ET by CMR

  6. baseboardking | Dec 25, 2004 01:09am | #21

    We have a shop nearby that makes plaster crowns & moldings-Felber Studios. Visited their shop; Lots of rubber molds! That's where the time and expense is. If you want to do plaster, you need the molds. They make a mock-up of wood, styro,etc, pour rubber over it,voila- a mold.

     

     

     

     

     

     

    Baseboard been VERRRY good to me
    1. JerBear | Dec 25, 2004 01:59am | #22

      I did this for a living for a while in NYC at a plaster casting shop.  We would make molds just like you said from castings of existing or make them up from wood mouldings or carve them from clay.   We would then  spray it with a separater, pour a moulding rubber around it and let that set to create the negative.  Then depending on how thick the rubber is...if it can stay stable when you do the actual casting or not... you may have to make another mould around the rubber out of plaster called the "mother mold", to set the rubber in and keep it straight and stable while casting.  The mix for casting is pure plaster to a thick pourable state.  Always use a separater like vegetable oil between the castings. 

      You can run plaster moulding in place if you want.  All of the advice here on the thread is fairly correct and everybody has their own way of doing it.  Just make sure you have straight wood "tracks" to guide your templated horse, and that whatever you are attaching your plaster to (mesh, burlap, browncoat plaster), is securely fastened to the framing of the cieling and wall.  To make miters while running in place is not easy and it's not that easy to explain.  You have to have a 'miter rod' that you run over the already finished crown and throw the wet plaster into place as you do it, you must also have a light touch and patience. This is why it's easier to attempt plaster mouldings the first time by casting them and then just cutting them like wood mouldings and affixing with a slip of pure wet plaster and then fill in the voids with plaster like you would with wood putty. The mix for running should be  two parts lime putty to one of white art, or casting plaster.  You can use plaster of paris if you want.  Also use a retarder when you do this....not too much as it weakens the plaster, you can use white vinegar, maybe a tbspoon per gallon of plaster mix for this.  The lime will also act as a retarder.  Get hydrated finish lime (USG) and just follow the proportion directions on the bag.  Soak it overnight and it should be the consistancy of sour cream. Always wear gloves while working with lime.  A good mason supply should have all this stuff.

      Good luck.  Let us know how it turns out. 

  7. migraine | Dec 26, 2004 02:40am | #28

    this company for detail work  They have 3-4 large catalogues of plaster and "old world" composite moldings.  I've worked on a few jobs with this stuff supplied.  None of their stuff was perfectly flat/staight.  everything was corrected on the installation by cutting and filling.  Their plaster work seemed to be made with plaster and a jute fiber for reinforcement.  The jute stuff was like the long wooden fiber material that you sometimes see in shipping/packing to prevent breakage. 

    http://www.jpweaver.com

    1. donpapenburg | Dec 26, 2004 07:28am | #30

      Thanks for the link . It was a little slow and did not work well when I tried it. Oh well I want to try to do this myself . A little experiance never hurt . You never know when a job might pop up that requires that skill.

      In a small mid west town it is tough to find tradesmen to do some of the finer craft trades.

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