Turtorial on casting your own bridge abutments

[slagpot]

Hello all,


I really got sick of paying for over priced resin bridge abutments, so i made some.I moved for New York to SC over ten years ago and one thing I miss is the the limestone walls used in NY & PA. I started by using pieces of old cardstock, cut to the desired height and width.
I then glued on the side peices so the plaster wouldn't run out the sides. These aren't as hard to make as you might think, there very easy to make.

Then I used rubber bands and clamps to hold the mold together. After the plaster has hardend for 10 mins, I removed one side of the mold. Then carefully using a dentist pick,carved the pennsylvania keystone out of the plaster. The real tricky part is to allow your-self time to work the plaster. So you have to work quickly, other than that its very easy to do. Even the beginners can do this ,to the seasoned modelers.

I'll post photos of the homemade molds later and the finnished abutments washed down with alcohol & indian ink.

Patrick
Beaufort,SC
Dragon River Steel Corp {DRSC}

 

[FiatFan]

Hi, Patrick.

Any pics yet?

Tom

 

[slagpot]

Sorry it took so long for me to reply back.

This first picture is of two cardstock molds of different bridge abutments. I used a pair of metal shears to cut the card stock,this is very hard to cut stuff. I made these molds with out the help of measuring another abutment,just think of it as {imagineered}.

This photo is after carvering the pennsylvania keystone {using a dentist pick} and the alcohol & indian ink wash. This is the easy part....the hard part was carving the stonework.The only thing to doing this project is to allow yourself time to carve,but if it drys you can always re-carve the spots you missed as in the next photo {the white lines}

Notice the white lines in this next photo....these are the re-carves I was talking about. Not to hard to do once the plaster hardens. If it is and you have one ...use a dremel tool with a engraving bit,this will surely do the job {but don't cut to deep}.

After this is all said and done weather the abutment to what you like and it will last for years {and save you some cold hard cash too}.

Tomorrow I plan on casting the large abutment in the background in the first photo. I'll post pictures of the whole process. One more thing....when mixing the plaster,mix it in a zip-lock sandwich bag.After mixing,cut a small hole in the corner of the bag and squirt paster into mold. Then tap the mold to release the air bubbles,let stand for about 5 to 10 mins,before removing the side of the mold for carving.Be sure to only remove half the mold,as this will help you move the abutment around without damaging it.

Patrick
Beaufort,SC
Dragon River Steel Corp {DRSC}
Making HO scale steel by the ton!!!!!

 

[zedob]

A zip-Loc bag!? I like that. :thumb: The good thing about that is that you've created a bottom pour device, which if done correctly will eliminate alot of the bubbles if you can let it sit for a minute to give the bubbles some time to rise to the top. I wouldn't mix in the bag, but mixing in a bowl then transferring should/would work.

I like your idea of keeping the casting in half of the mold while working. I don't use the same procedures for casting my stonework, but I highly recommend using any devise to keep your work safe. Believe me, I knocked one of my carved stone slabs off of my workbench and it took me a good hour to get over that, seeing that I spent days on it and I was almost finished. :cry: I was able to save it,:thumb: but it put me behind by another two days.:curse:

I don't use a dental pick for my work because I find that they have too much "spring" and can hang up in the grooves then give way in-turn making a big gouge across a stone that really didn't need it. :curse: A Dremel type of handpiece is the best way, but the amount of dust it produces can be a hazard to your health. I wouldn't use one unless a mask, or a vacuum system is used.

If you find that the plaster is getting hard before you can finish you can wet the immediate area where you were carving and the plaster will soften up some.

BTW, what kind of plaster are you using?

Also, if you use acrylic paints (Micheal's or Hobby Lobby cheapo) you can thin them into washes that can be applied in a random pattern to give the stones some "independence". Then come back with the Ink wash to highlight the grooves/joints.

 

[Russ Bellinis]

I buy plaster for use in making plaques and animals and such for a children's summer camp. I recently had to change suppliers, and my new supplier reccomended using Hydrostone instead of Hydrocal. In their instructions they said to always add plaster to water, never water to plaster. You need to measure the amount of water precisely to the amount of plaster you are using. You sift the plaster into the water to avoid clumps. They suggested that using an egg timer to allow the plaster to soak in the water for 2 minutes before stiring would keep the plaster from forming air bubbles. It was the same instructions for both Hydrocal and Hydrostone. The Hydrostone is about 10 times stronger than Hydrocal when it cures.

 

[Canopus]

My only gripe with plaster has been that it is too brittle once it has cured, so I might try this hydrostone stuff...

FYI, there are lots of resin moulding kits out there - if you wanted you could use one of these to take a rubber mould of your plaster abutment, and then produce them in resin. You could even sell them if you wanted. Neat eh?

 

[zedob]

I buy plaster for use in making plaques and animals and such for a children's summer camp. I recently had to change suppliers, and my new supplier reccomended using Hydrostone instead of Hydrocal. In their instructions they said to always add plaster to water, never water to plaster. You need to measure the amount of water precisely to the amount of plaster you are using. You sift the plaster into the water to avoid clumps. They suggested that using an egg timer to allow the plaster to soak in the water for 2 minutes before stiring would keep the plaster from forming air bubbles. It was the same instructions for both Hydrocal and Hydrostone. The Hydrostone is about 10 times stronger than Hydrocal when it cures.

I use Ultracal-30 for my work, which is srong but not as hard as I would have thought considering the fact that when people say Hydrocal, the first thing that comes to mind is hardness. The dental die stone I use for my patterns is much harder. I always add plaster to water, but may end up adjusting the consistency by adding plaster to water and letting the plaster soak for a minute or two helps in de-airing. Air bubbles are not much of a problem because I use a vacuum mixer that just about removes all entrapped air. Any bubbles that may show up are due to a surface bubble in the surfactant. The trick to get rid of those is to slap the mold down on the workbench to pop them. I use silicon rubber molds, so I can do that, but I don't think it would be a good idea for cardstock form.

 

[slagpot]

Hello all,

Here is the whole process from start to finnish. The first photo is of the mold clamped together,ready for the plaster mix.

This next photo is of the plaster mixed in a zip-lock bag.

The next photo is injecting the plaster into the mold,be sure to tap the mold so the plaster will fill all the voids.

This photo is after about ten mins forming in the mold,with one half of the mold removed,ready for carving.

This is the carving process...it doesn't take to long,but you must work quickly.

This is the finnished product after about 7 mins of work carving.

This photo is of the indian ink and alcohol wash hard at work.You could paint each stone with acrylic paint as Zedob talked about. This would look much better using acrylic paint.

And this is the bridge abutment fully carved and washed.

Cardstock....free
Plaster of Paris.....about $8.00
Having the coolest hobby in the world....Priceless

For every-other hobby theres VISA

Hope you folks enjoyed this little Turtorial...there will be more to follow,as soon as I find something else to make from scratch.

Patrick
Beaufort,SC
Dragon River Steel Corp {DRSC}
Making HO scale steel by the ton!!!!!