For most modeling work you can use plain old plaster of Paris. Hydrocal is only if you need very hard, strong plasterwork. If you are casting structures, hydrocal may be better (which is ironic since plaster of Paris was used to make architectural details) but for most scenery work regular old plaster will work just as well.
Dave H.
Dave H. Painted side goes up. My website : wnbranch.com
For the contrarian view: I like the strength of hydrocal for hardshell work. I have cracked plaster hardshell on my older layouts that used Plaster Of Paris.
Skip the Woodland Scenics and go for the big bag at construction stores carrying lath and plaster supplies. There is usually one place in most medium sized cities that carries this stuff (HD ain't it). Another option that I like is plaster cloth (again skip WS and buy in bulk on Ebay) with a nice coat of hydrocal on top.
Here is an example of my work using hydrcal...You could stand on portions of this rockwork. It took a sledge to break it up when the layout came down.
Have fun,
Guy
see stuff at: the Willoughby Line Site
Roger Hensley= ECI Railroad - http://madisonrails.railfan.net/eci/eci_new.html == Railroads of Madison County - http://madisonrails.railfan.net/ =
Hydrocal comes in 100# bags. It is listed as a 'gypsum cement' and comes in several types, all of which are fine for scenery work. Hydrocal, Ultracal, Tuff Stone, Ultracal, and Fast Cast are USG products. The setting time is 20-40 minutes. These products dry with a very hard shell when used for scenery. The bad news is that they do not take stains very well.
Myself, I use medical plaster wrap over a mesh of cardboard strips to build my basic land forms. If I need more strength, I 'paint' the land form with Hydrocal. I later 'paint' the entire area with Plaster of Paris, and cast all of my rockwork with Plaster of Paris. As I mentioned, Hydrocal is very tough and does not take my rock stains very well.
Back in the late 60's, I used Hydrocal soaked paper towels to build land forms and it was a very slow/messy process. The plaster wrap is much faster and for the most part, I have not had any 'strength' issues. I was 'painting' large areas with Hydrocal for additional strength, but the last 14 feet of scenery has no Hydrocal on it and I am satisfied with the overal strength of the 'bluffs' I have constructed.
BTW, I have been using 'Sheetrock' brand joint compound($6.71/18# at Menards) rather than Plaster of Paris. You can get it in various setting times(20 min - 225 min) and is sands/takes stains quite well. Normal pre-mix joint compound dries very hard and will not take stains. The long working time(I use the 90 min) allows me to carve and work-in my rock castings, and not have the material set-up all at once in my mixing bucket! I was looking for Structo-Lite, but none of the 'big box' stores seem to carry it. The 'Sheetrock' brand seems to be available in my area(Rochester, MN).
Jim Bernier
Modeling BNSF and Milwaukee Road in SW Wisconsin
Does the setting time of Hydrocal (non WS) versus WS lightweight hydrocal differ? I find the working time too short for a lot of work I would like to do on my layout. Is there any way to slow the working time? Drying time I don't care about, it can take as long as it wants.
Isn't hydrocal the stuff dentists use to make mouth/jaw/teeth models?
de N2MPU Jack
Proud NRA Life Member and supporter of the 2nd. Amendment
God, guns, and rock and roll!
Modeling the NYC/NYNH&H in HO and CPRail/D&H in N
Jack,
Typical setting time is about 20-40 minutes(depends on the 'mix' of water/material & if vinegar/salt was added to the mix). And yes, it has been used for one time casting molds. Ultracal has been even used for short run stamping!
'Lightweight' Hydrocal from Woodland Scenics may be one of the polymer filled versions of Hydrocal(or maybe W/S is mixing in something). I have used 'tubs' of the W/S product and have found no difference. As far as weight, I never measure that(I have no idea what my layout weighs).
Jim
rogerhensley wrote:Hydocal can also be found under the name "Ultracal 30" it comes in bulk.
jackn2mpu wrote: Is there any way to slow the working time? Drying time I don't care about, it can take as long as it wants.
Is there any way to slow the working time? Drying time I don't care about, it can take as long as it wants.
Adding a bit of vinegar to plaster o paris slows the drying time. Probably work for hydrocal too. (try a small batch first though) I add 2-3 table spoons of vinegar to a half gallon jug of water and use that to mix my plaster.
loathar wrote: jackn2mpu wrote: Is there any way to slow the working time? Drying time I don't care about, it can take as long as it wants. Adding a bit of vinegar to plaster o paris slows the drying time. Probably work for hydrocal too. (try a small batch first though) I add 2-3 table spoons of vinegar to a half gallon jug of water and use that to mix my plaster.
From the far, far reaches of the wild, wild west I am: rtpoteet
I use a product from Canada Gypsum (also available from USG) called Durabond. The name is followed by a number, such as Durabond-90, which represents the setting time, in minutes. I believe the fastest is Durabond-20. It comes in 1 lb. and 5 lb. boxes and in 33 lb. bags. While it is a patching plaster, it's sometimes used as a joint compound, although seldom for the finish coat, as it dries very hard and is tough to sand. It will set in the designated time regardless of how thick or thin you mix it. I used it over screen for my basic landforms, then coloured it with interior latex house paint, mixed about 50/50 with water. Thinning makes it easier to apply, and it soaks right in.
The stuff that hardens in the mixing container can be broken up with a hammer and used as rip/rap and sub-fill for the track and structures. I sprayed mine with a thin wash of black acrylic:
Durabond can also be used for casting bridge piers and abutments, using simple moulds made from sheet styrene (the info is a few posts down in the link). I stained mine with a wash made from PollyScale paints (still need to add rust stains).
I also used the same Durabond to make the "water" in the rivers. It was painted with the same type of paint as used for the landforms, unthinned, then covered with three coats of high gloss, water-based urethane:
jrbernier wrote:... Normal pre-mix joint compound dries very hard and will not take stains.
... Normal pre-mix joint compound dries very hard and will not take stains.
I used regular pre-mixed joint compound to make roads, then stained it with thinned mixes of PollyScale paints. It took the stain well, but the road surface is very soft. The "patches" were applied to areas that actully needed repair:
Wayne
This is an old thread but very good info.
Lynn
Present Layout progress
http://cs.trains.com/mrr/f/11/p/290127/3372174.aspx#3372174