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What follows is a basic, easy to understand (I hope!) tutorial on how to assemble, paint & weather a hydrocal structure kit. If you have any questions please feel free to contact me, either via email (downtowndeco@montana.com) or call 406-821-0181 9/5/m/f Mt time.Basic overview of hydrocal kits. OK. People often ask me why would they want to build a hydrocal kit when they could just buy a Walthers or DPM plastic kit? While those two manufacturers make great products, as a small manufacturer/craftsman I can offer something that they cannot. An original pattern that is hand carved one brick, one stone at a time. The larger manufacturers almost always use injection molded plastic as their method for producing kits, and to create the tool and die work with this amount of surface detail is simply cost prohibitive. As you can see, when the patterns are all hand created their is a certain “organic”, real look to the model when finished. I can add chipped and missing bricks, cracks and other surface weathering that you’re just not going to find in a plastic kit. Basically you just end up with a much more realistic looking model IMO.What do you see when you open a plaster kit? Usually there are 4/6 hydrocal castings, plastic windows and doors, signs, styrene for the roof, misc. small details & a set of instructions. The kits are simple, yet look great when finished properly. The detail is all cast into the castings. Most of the “work” is painting the structure. I call that the “fun” part. This is the HO Scale Addams Ave. Part One kit.

The first thing you need to do is to clean up the castings & remove any excess flash. Because the parts are hydrocal and not plastic or resin, in most cases all it takes is a few minutes with an emery board, a sanding block and/or an x acto knife. Make sure the bottoms of the castings are flat and that there is no flash where the walls join. If I need to make sure the bottom of a wall is flat I will often just lay a sheet of 60 grit onto my work bench and slide the part back and forth over it a couple of times to make sure it’s flat.

An important step is to “test fit” the plastic doors and windows before you get the building assembled and painted. If you don’t you might find that after the building is all painted that some of the parts might not fit because the openings needed to be cleaned up and perhaps enlarged a hair, then you’ll mess up your nice paint job & it will need to be touched up. When hydrocal dries it shrinks a tiny, tiny bit, and while I always try to take that shrinkage into account when creating the master patterns, it’s not an exact science. So test fit the doors and windows now, and then set the parts aside until later. I use an x acto w/a #11 blade or, if needed, an x acto w/a small chisel blade to shave off a hair off an opening.

This isn’t really that big of a job. From beginning to end it only took me about five minutes to clean up the flash and test fit the parts for this kit.

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I prefer to use 5 minute epoxy to glue the hydrocal castings together. I’ve heard from guys that like to use white glue, yellow carpenters glue and ACC super glue and while any of those will work, I’ll tell you why I don’t like to use them.If you use white glue (such as Elmer’s or Eileen’s Tacky) you will have to wait overnight for each joint to dry, plus if you use a lot of water in your weathering process the glue may soften and the joint may fail. That’s bad.I think most yellow “carpenters” glues are waterproof but you’ll still have to wait over night for each joint to dry. I just don’t have that much time. : )ACC “super glue” will work, IMO however, it is not the ideal glue for hydrocal because the hydrocal is so porous. Sure you could use gap filling super glue or prime the castings before hand but that just sounds like too much work for me. The other thing is, for me anyway, is that super glue always seems to “go off” or set just as the wall wiggles and it’s crooked. It’s all or nothing w/ACC.So I use 5 minute epoxy, and mix up very small batches and do one wall at a time. That way it gives me a few minutes to make sure my wall is straight, true, and where I want it, but by the same token, in 5/6 minutes I can move on to the next wall and get that one up & in place. Usually within 30 minutes I can have the basic building glued together and I can move on to the painting.This is important. Unlike wood, cardboard or even plastic, hydrocal has no bend or give. You can’t bend or “tweak” any of the parts into place. So if somewhere along the assembly process you were off by a bit, when you get to gluing the last wall in place you won’t be able to “squeeze” it into place. You’ll have to either do a bit of sanding to get the part to fit, or, if you somehow ended up with a gap, fill or disguise it. No biggie, it’s just something to be aware of.Because you will sometimes have to sand a bit of the edge of the last wall to get it to squeeze into place, I always have you assemble the castings in a certain order, with the wall least likely to be seen by your viewers (usually, but not always, the back wall) to be the last to be put in place. That way if it’s less than perfect at least it’s not staring you right in the face on the front of the building. When I glue my castings together I try & not have any squeeze out onto the “outside” of the model where it will show. The easiest way to do that is to not put the glue right next to the very edge of the castings. Leave yourself a little “squeeze” space in case some of the glue wants ooze out of the joint. In this case I have marked w/a blue marker where the glue should go.

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Only mix up a tiny bit of the epoxy at a time. Here I’ve mixed it up and added my first wall. I used a piece of styrene to make sure the side wall was “square” w/the front wall. I propped it up w/a roll of tape & “babysat” it for a couple of minutes to make sure the wall stayed where I wanted it.

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Next I added the other side wall.


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When I test fit the rear wall I found that I needed to remove a tiny bit off of each side to get the part to ease into place. Remember, do not try & force the part into place. You will break it. I gave it a few swipes with a sanding block & then glued it into place. You don’t need to worry too much now about any small gaps or seams, if you’ve got them we can deal with them later in the build.

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Finally, I carefully cut & test fit, and then hot glued in a few scraps of cardboard to add strength to the structure.

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Sealing/priming the castings.

First, there is not a right or wrong way to build models or enjoy our hobbies. What follows is strictly my opinion based on painting hundreds of hydrocal castings;

I always recommend at least “sort of” sealing plaster castings to remove some of the porosity. Perhaps “priming” would be even a better word than sealing. I use flat white spray paint. A couple of light coats. That way when you apply either your paint or stain it will flow on more naturally and evenly than if you applied it to raw plaster. It allows you to get a smoother looking, more even tone to the base coat. You also have a little bit of time to “work” the color. You have less of a chance of the color coming out too intense or dark as well. Finally, when your painting/staining is all done, you can ever so lightly “buff” the surfaces with very fine steel wool or polishing sandpaper to make all of the details and highlights “pop out”. It’s sort of like dry brushing but instead of adding paint you’re taking just a tiniest bit of paint off the tops of the high points. It really “makes” the model IMO. Understand that I’m not saying to seal the plaster so that is like plastic or resin, but rather, just enough so that each and every brush stroke does not get soaked in instantly.

Not sealing the castings, IMO, increases the risk of the following happening: A blotchy looking, uneven finish that looks “brushy”. It also increases the chance that you’ll end up with “solid looking” dead toned walls, rather than richly toned parts that look like they have natural age, patina and years on them. You don’t have any time to “work” the color you’re adding, as each and every brush stroke is soaked in instantly. True, you can “build up” colors, one thin wash at a time, but you can do that ever better when the castings are sealed because you can control it so much better. Also, unsealed you have to wait long periods waiting for the castings to completely dry so you can see what the actual color looks like. Sealed you can put a fan or hair drier on the parts & see what you’ve got in a few minutes.

I’ve tried both (sealed & unsealed) & in my opinion sealed works best and give you better results. Tom Yorke & CC Crow have recommended sealing hydrocal castings in the past as well, and both of those guys have slung their share of plaster over the years.

I think that usually (and I could be wrong) is that the guys who swear by unsealed castings have not ever actually tried to paint/stain sealed castings before. It sort of goes against their natural intuition. I mean, why take one of the unique properties of hydrocal away? After all, isn’t that what makes plaster parts look so cool? Again, IMO, not entirely. Usually what makes a plaster kit look so much more realistic is the original, hand carved master patterns.


OK, let’s get some color on this thing! First off I gave it 2 or 3 medium/light coats of flat white primer. I used Krylon primer but have used other regular non primer flat white spray paints with good results too.


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 I let it dry for an hour or so (over night is even better) & then got out my first two colors. I prefer a more “orangish” brick color, so I used Folk Art brand Terra Cotta # 433 as my base. This is a cheap acrylic craft paint. Apple Barrel and Cermacote are similar brands & have similar colors.I used a scrap of cardboard as a pallet, a .49 “chip” brush & some water to lay this first color on. I did it dirty, wet & quick. the most important thing is to not put the paint on too thick (unthinned it’s almost as thick as Elmer’s glue) and that your brush strokes all end up going vertical rather than horizontal. I’d say I had the paint thinned about 75% or so.I paint the whole thing, rather than trying to dinky bob around the details with a small brush. I’ve found that if I try & do it that way the structure can look “brushy” rather than having a nice, even tone to it. Make sure you get all of the cracks and crevices of the windows, door jambs and trim. you don’t want any white showing. Also paint a bit around the inside of the top of the building to get a little color on that as well. The whole thing took about 5 minutes. The paint is still wet in this picture.


I also used a bit of Raw Umber to “break it up” a bit. Here’s where having the castings primed really works to your advantage. Because each and every brush stroke does not soak in instantly, you can “move the paint around” a bit, and add more paint if needed, or scrub it off with a little water if you got it on too thick. Again, vertical, not horizontal.

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Next I painted the concrete & stone sections Poly S Concrete color. I like the Polly S for this because it covers and flows on well.

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I then masked off the tile section on the pawn shop…

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…then misted it first with the flat white primer spray paint…

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…then when that was dry I spray painted it Krylon3509 Jade Satin.

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I then masked off & spray painted the “Marble” on the liquor store flat black. Satin or even a slight gloss would have been better but I didn’t have any on hand & was to lazy to run into town & get it. : )

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I spray painted rather than brush painted the tile & marble sections because it would be smoother & introduce a new finish or texture into the building.

We’re getting there. Once we get past these basic undercoats we’re really going to start to get the fun part.


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The next thing I did was to paint some of the individual bricks a little lighter, and some of them a little darker. The way I did it was to start off with the base brick color, and then add a little white to one batch and a little raw umber to the other. Using a small brush and a magnifier, I had at the bricks for about 15 minutes to add some contrast to the finish. The trick is to use a brush w/a good point and to add enough water so the paint goes on easy. Too thick and it will be “gloppy”, too thin and it won’t cover or will flow into the mortar more like a wash, which isn’t what we’re going for here. I always a paint a few of the “corner” bricks in addition to the ones directly on the front and sides as well, that always seems to look pretty good.

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This is more an undercoat or “base” for the final weathering stage than something that will be right on top & prominent. Most of these bricks will covered up or blended in in the end, so don’t waste your time painting hundereds of individual bricks, IMO it’s not worth the effort.

I used to work in Hollywood in the film industry as a scenic artist, which is basically a set painter. That means I had to make things look old, or new, or rusty/weathered/whatever. When I first started I worked at Roger Cormans studio. He’s known as the king of the B movies, and let me tell you, the “B” is does not stand for “Big Budget”. We had to work fast, cheap and dirty, and it still had to look good. I learned some tricks along the way and one of them was never waste any time on something that’s never going to be seen anyway. That is just an exercise in wasting time. So in the case of these bricks, don’t waste time being overly fussy or a perfectionist. Do what you can in 15/20 minutes and then we’ll move onto the next step.

I also painted the inside edges/openings of the door/window frames flat black. That way later on when we add the doors/windows we’ll have a little wiggle room if one of the parts is a bit on the loose side.

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On to the stone. I used very thin washes of Raw Umber, Burnt Umber, Raw Sienna, Black & White to color the stones. I kept the colors pretty light & even left a lot of them the base concrete color. When I add the weather/aging washes over this it’s going to look a lotbetter than it still does in this raw stage. Time spent on this step? Ten minutes at the most. You don’t really need to stain/paint each and every stone to get a good effect. In fact, there should be a “sameness” or continuity between the stones. If you make them all wildly different it won’t look natural. The wash will tie these all together in the end.

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The next thing that I did was to add a wet, sloppy Raw Umber & Black wash to the entire structure. I used a 2″ (I think) chip brush & plenty of water. I did not want to apply this perfectly even, because if I did I would be missing an opportunity to add a bit a character. So I made the black heavier in some areas, lighter in others and so on.A couple important points about adding weathering via a wash.Put it on wet so that it can naturally flow from the top to the bottom of the structure and so that you have a little “work time” to push the colors around where you want them. Again, if you prime your structure you can play with it a bit. if not, every stoke will soak in instantly.Don’t leave a drip “hanging” halfway down the structure, it does not look natural.I stick mainly to Raw Umber &with a bit of Black here and there for variety.Not sure if you’ve added enough? Let it dry. Put a fan on it or use a hair drier to get it to dry quicker.


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When it was totally dried I ever so lightly “buffed/rubbed” the structure using 1500 grit polishing sandpaper. It’s sort of like dry brushing in reverse. Rather than added more paint you’re just taking a tiny bit off of the high surfaces. This really makes the detail stand out. If you knock off a bit more than you wanted to in a spot or two simply go back & touch it up w/a small brush & a bit of Raw Umber. A little of this technique will go a long way, so don’t over do it.


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After the wash dried I it just didn’t look “gritty” enough for me, so I wet the front down and gave it a heavier wash using the black acrylic. It went on very wet, and while I wanted it to “run down” naturally, I knew if I stood the building upright (like it would stand on the layout) almost all of the wash would run right off the building & onto my work bench. So what I did was wet the facade, give it the black wash, lie the model on it’s back (w/the front facing the ceiling) and then I stuck a metal bottle cap under the back of the building placed just so to tip the model slightly forward. That way the gravity moved the “weathering” naturally from top of the building to the bottom but since the building was tipped just ever so slightly forward most of the wash stayed where it was suppossed to.

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I spray painted the doors and windows and then, when dry, gave them a heavy wash w/the black acrylic. The wash is still wet in this photo.

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Next I glazed the doors and windows by cutting small bits of clear styrene & gluing in place using liquid styrene cement. I then cut out some of the ads and added them to the inside of the glass. Finally, I glued the plastic parts in place with a few small drops of super glue.



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Some, but not all, of my Downtown Deco kits include laser cut, self adhesive sign “stencils”. They’re used to “paint” a sign onto the side of eth building. In the end it looks like a sign painted on brick because it is a sign painted on brick.

The most common type of sign is white lettering on a black background. I start by masking off an area that I can spray flat black.


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I next sprayed it using a rattle can. It does not have the to be perfectly black, if a little of the brick is showing through that is OK.

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Next I peeled and carefully positioned the self adhesive stencil & pressed it in place.

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The centers to the O & A’s “float” so you need to peel them off of the backing, position them, and carefully press in place. I use the point of a hobby knife to hold and position the tiny pieces.

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Next I lightly spray painted the wall flat white. Easy does it, as the lighter and more faded the better.

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Carefully peel off the stencil…

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Next I “dirtied the sign up” a bit & brought it down a few notches by first giving in a wet black/raw umber wash. I made sure that in a place or two there were noticable streaks of the black.

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When dry I ever so lightly buffed this wall w/the 1500 grit polishing sandpaper. When I did I knocked off a bit too much off of a couple of the high points (exposing the white plaster) and I needed to go back w/a tiny brush & some raw umber to hide them. I still think this is an important step though.

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Finally, using one of my fingers and some brick colored chalk I sort of rubbed the area a bit to get it all to blend.


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The next thing I did was to add some roof supports using a few pieces of scrap styrene. I used super glue & glued these about 1/4″ from the top of the walls.

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Next I glued the styrene roof in place.

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I cut a single piece of black construction paper to fit, then drew on some “tar lines” using a black Sharpie & a straight edge.

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I misted the construction paper with flat dark brown and light tan spray paint and then glued it to the roof.

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 Next I painted the faux “walls” a concrete color & then glued them into place. I brushed in some dark black/brown chalk around the edges.

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The last step for now is I sprinkled the roof w/just the finest dust of a rust colored chalk & added some extra texture w/a few ribbons of white glue (still wet here).

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In no particular order here’s what I did to age/detail the roof:I added a few more lines/small puddles of white glue to add a new texture & a variation to the sheen of the roof. In other words, while 99% of it is flat (dull) by adding a few spots of white glue it sort of looks like gleaming tar or puddled water.I painted and added chimneys and a couple AC units.I ripped open one of those shredded paper filled shipping envelopes and glued some of the paper pulp/shreds to the roof to look like old newspapers or whatever. Likewise I added a scrap or two of brown paper bag to simulate a part of an old cardboard box.I added a couple of small pipes to the roof using 20 gauge wire, then snipped 4 or 5 small piecs and left them on the roof in a stack like a workman had left them there (or whatever).I made an old garden hose out of 22 gauge wire, painted it green & left that up there as well. Why? Why not? It’s one of those stupid little details that visitors to your layout will notice & get a kick out of. They won’t give a crap that you spent six months gluing wood shingles on one at a time but take 5 minutes to make a fake hose out of a piece of bent wire & you’ll get “Well look at that….!!!”Finally I “flicked on” some watery stains using various shades of black brown.

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Adding the rest of the signs. I apply signs a couple of different ways. If I want to make a sign look like it was painted on the brick I simply cut the sign out, apply white glue to the back of it, and then press it in place. When applying the glue I quickly spread it on using a scrap of styrene as a sqeegee.

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After I have it firmly pressed in place, a place a piece of clear plastic over it and run my fingernail along each and every horizontal brick row, then generally burnish it a bit more. The white glue softens the paper (eliminating the need to sand the paper thinner) and the plastic protects the fragile paper so that you do not rip it while burnishing it in place. I’m lazy & this takes all of 5 minutes to make it look decent.

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If I want a sign to look like a tin or metal sign I laminate (glue) the paper sign to a piece of .020 styrene, then glue it in place. If it’s a small sign I will often just stick it to the building using a school glue stick. Again, I’m lazy. : ) This is what the signs all look like before I age them a bit.

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Finally, I aged the signs a tiny bit by just rubbing on a little black/dark brown chalk. Less is more here. I tried to make some of the dark stains that were already present on the brick walls carry on up and over the signs I applied.I also made some quick & dirty drain pipes out of pieces of 18 gauge floral wire. This killed two birds w/one stone, as it added a small bit of detail plus it covered up the seams where the walls joined.

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If you have any questions at all please feel free to call or email me. Cheers!
Randy Pepprock
Downtown Deco