Proper mixing of Hydrocal?

[jwr_1986]

I was hoping someone might be able to tell me the proper ratio of Hydrocal to water. A friend of mine recently gave me a 100 Lb. bag of hydrocal [}:)] (I really can't stande emoticons but I couldn;t resist) but he didn't remember the right proportions and the bag is brown with the word Hydrocal stenciled on so it offers little help. Any response would be appreciated.

Thanks,
Jesse

[cacole]

Just put some in an empty can or jar, add water, and mix while adding more and more water until it gets to the consistency of cake batter. If you get it too wet, it will still harden but just take longer to begin setting up. Too thick, and it can't be spread evenly. There is no actual "formula" that I know of, because the thickness is going to depend on what you are using it for.

[bogp40]

Jesse,
I always find it much easier to add the powder to the water, this way you don't end up w/ dry or clumps in the bottom of the mixing container. The only disadvantage of this is knowing how much water to use for the mixed amount required. After a few tries you will get the hang of it. When ever I mix any product whether mortor, concrete, grout, or plaster adding dry to water gives a more even mix with less effort. As cacole says, there's no real formula, trial and error for what works best for you. Remember that trying to use hydrocal for base coats of hardshell on screening or foam, you have very little working time. Hydrocal is best for rock castings, and the like. If you use skimming plaster(type for pastering over blue board), unical, diamond, etc, you have 15-25min working time and can be dressed or feathered with an old paint brush and water.
When casting rock, retaining walls etc, try adding color so you are not trying to hide the pure white of plaster. I use the powdered masonry dyes used to color mortor or concrete. They can be found at any stone/ masonry supply. The dyes come in various colors, with black, brown and red the most commonly stocked. They are formulated exclusivly for masonry products and have little or no affect on the drying or hardness of the plaster. Mix color to the dry plaster for approximate dried/ cured look. When wet a touch of gray will change to black (think of tile grout colors). My final top coat of scenery hard shell plaster is always colored, brown for earth add black for yard and industrial areas. Experiment with the products before jumping into a batch destined on the layout.
Good luck and hope this helps.
Bob K.

[Anonymous]

Jesse,

I used a measuring cup and a yogurt container (small) to measure the plaster mix. I used the bottoms (cut the tops off) of gallon milk jugs and put two yogurt containers of plaster to one pre-measuerd cup of water. You will have to experiment with the mix to get one you like. Don't add water or plaster later in the mixing process-it screws up the cure. After you figure out the mix, use the same one over and over and assembly line it. I would use 10 or 12 cutoff gallon containers in an evening. The plastic makes it easy to clean by flexing and cracking cured plaster out off the containers. Expect to make a mess....I have plaster shoes, pants and jacket which I keep outside in the trainroom....Nothing sets the better half off like bits off plaster on the couch etc...

I colored the plaster after it had set in the fashion of water color painting: Adding washes to get thre darkness I desired. I didn't like pre-coloring of the plaster because it made the color too even which I found unrealistic. If you add color to the plaster experiment....Nothing like a dark brown mud mountain when you wanted granite. Remenber you can always add more plaster or take a hammer and break it out if you don't like it.

Guy

[Anonymous]

USG's instructions are on the left, down a ways under tools.
http://www.plaster.com/index.html

[jtatum65]

jwr i too obtained a 100 lbs bag of hydrocal. the mixtures i use is as follows....

For rock molds and general land forms mix 2 to1 (1cup hydro to 1/2cup water)

For covering plaster cloth or papertowels 1:3 mix (1/2cup hydro to 1/3cup water) that makes a nice soupy workable mixture.

also i dont know which hydrocal you have but i am using statutory hydrocal is more a grey color and about twice the weight but other then that i found it suitable

[jwr_1986]

Thanks everyone, I appreciate all of your responses. Some the ideas for dyeing the plaster are great. jtatum65, my bag is the typical pure white variety. One of our club members heard about my recent acquisitiion and handed me a giant bag of rock molds to play with. Well off to experiment, sound a little messy but alot of fun.

Thanks again,
Jesse

[Anonymous]

When the time comes for needing a faster set-up. It's said you can make "seasoned water" by adding small amounts of Hydrocal, to the water your going to be mixing into the dry stuff. It was something like a teaspoon, "IF" I remeber right.....

[cwclark]

the mixture is 2 parts plaster and 1 part water..if you don't want it to set up quickly, add a teaspoon of vinegar per cup of plaster ..it won't set up as fast so you can work it...another tip is to clean the container well after you've made the pour...left over plaster in the container will make the next batch you mix up set prematurely chuck[:D]

[Anonymous]

Can you add pigment to it??

[bogp40]

QUOTE: Originally posted by D_Davis

Can you add pigment to it??

Be careful what you add to color plaster, some use latex paints or the Sacrete concrete color, I have found that these tend to affect the curing and/ or hardness of the plaster. Experiment first, you may find a product that works good for you. As in my previous post, I recommend the masonry dyes. I only use them to basically give some color before final paint or washes. An example is simulating asphalt roads or parking lots. Mostly black with atouch of brown added to the plaster(dry) resulting color before adding water will be very close to the cured/ totally dry roadway. Many times all that is needed to fini***he road is details- patches, man hole covers Fine screen cut and set into plaster a realistic sewer or drain. Give it a try.
Bob K.