LIght Weight Hydrocal mixing small batches

[inobu]

This stuff has been a challenge. Trying to mix small batches has been a problem and now I think I got a handle on it. It goes against the norm (adding hydrocal to water little at a time) but it seems to work better. The problem is surface tension. Some of the hydrocal mixture will not break the water tension (the power bubble) therefore preventing a good mix leaving clumps. 

 

It seems that the answer is adding water via a spray bottle. The spray bottle will create a mist which is atomized water. The hydrocal will absorb the water faster and you can control the water distribution in minute portions. This works for portions less than a oz. I think it will work better in larger quantities too you just need a larger spray bottle. The key is breaking the water tension by creating little droplets.

 

I have taken small cups of hyrdocal and misted the power, wait a few minutes and the power will soak it up. It seems gravity aids in the water distribution into the hydrocal. LIke watering the lawn

 

I casting portals now and created my own molds. the problem is I used silicone modes and the water beads up no matter what. The water wetting theory is not working to good with the silicone molds.

 

 

 

 

 

 

You can see the difference in the mixture. The center one is from the sprat bottle. I am able to control the consistency and yield a better mix. The retaining wall is from a poor mix and the one on the right

is from just a pour without slamming in on the table to fill the air voids. Slamming the mold on the table seems to pack or increase the density which seems to feel better.

 

My next option is to us a brush to apply the first layer of hydrocal and then pour the rest then slam it (slight exaggeration). I cant believe how long this is taking

 

Oh well, hopefully the tips will help out

 

Inobu

Edited July 27, 2016 by inobu

[inobu]

Funny the retaining wall could work as it look weathered with the possibility of paint flaking off in the center.

 

Inobu

 

 I was looking at the retaining wall and the texture looks just like cinder blocks. I wish I knew how I did it. Its the mixture. I has a light mix. oh well 

Edited July 27, 2016 by inobu

[cteno4]

Inobu,

 

Great work! Yes I've done some hydrocal and it does not mix like cement! I was painting mine on stuff for scenery and casting rock (so bubbles didn't matter) but remembered that bubbles always seemed to form on the surface though.

 

What were you using for mixing? Did you try a small paddle mixer on a drill? Migh help blend water in faster as well but may intoduce more bubbles if too fast.

 

Quick look around it looks like plasticizer may help, along with your slamming! Also some look to use 50/50 wind exit for mould wetting, that's more than I've ever seen in a wetting agent!

 

Looking forward to your experiments! Great stuff!

 

Cheers

 

Jeff

[inobu]

Hey, Jeff its crazy what is being left out of the directions. There is so much more to it than just add water.

Hydrocal reacts to mixing. It can sit for a half hour if you don't touch it. When you start mixing it, it starts it pot time. The longer you mix it the quicker it will set up.

 

I tried a little paint mixer and it would kick in unbalanced and create hard and soft spots.

 

I use a cake spatula and its working.

 

The spray bottle works really good you can really control the consistency and vary the density. The cure time varies with it 

 

I can't use the wetter process because the silicone just causes it to bead up and it turns into a bubble.

 

The brush was a big fail because the hydrocal just got into the bristles. It works for the larger molds but no go for the smaller detail molds.

 

I was able to minimize the bubbles by running a blunt stick through out the mold and then drop the mold flat to shake the bubbles to the surface. I was able to get two portals with minimal bubbles so I go with it. It would have been easier and faster to just buy the portals from Woodland Scenics instead of making my own but I guess I have them for ever now. 

 

next is the rail road crossing. Hopefully that will be faster.

 

Inobu  

Edited July 28, 2016 by inobu

[cteno4]

Inobu,

 

Ahh now you say that I remeber that with the mixing. It's been a while. Might look at the plasticizer as it does sound like it helps limit the bubbles along with the heavy 50:50 windex wetting agent on the mould, that seems to lead to smaller sized bubbles that may be what you were looking for with the cinder block look you got on one.

 

These things are a lot of trial and error and experimentation to figure out what works best! Good luck with it! Good on yah for working at it.

 

Jeff

[inobu]

Good Casting

 

Well, finally figured out how to get a good casting bubble free. In the previous post I mentioned the slamming of the mold to force the bubble displacement. If was difficult slamming the mold on the table so I had to modify the action. 

 

Here is what worked and the results were two fold.

 

I placed the mold on a 12"x12" (305mmx305mm) 6mm PVC board and held it up a few 2ft or 600 mm above the ground and let if drop flat onto the floor. The impact caused the bubbles to rise or burst. The second effect was the compression of

the hydrocal. It increased the density of the mold. It worked really good.

 

 

Notice how the bubbles were eliminated and even the density is prevalent. So far I'm satisfied with the results I just need to wait for it to finish curing.

 

Much better

 

Inobu

[inobu]

Final Synopsis

 

After a week of testing and experimenting I was able to create good casting of my portal molds. In one respect it would have been cheaper to buy the portals and move on but learning how to cast hydrocal consistently  will prove useful in the future. If you were following along in the post I had issues with the mixing of hydrocal, the mixing process and the problem of bubbles in the casting. After two boxes of Light Weight Hydrocal and a week of playing I can yield casting that are bubble free and a little denser in form.

 

Taking note to Jeff's suggestion of the 50/50 mix for a water wetter I increased the about of detergent in the water wetter along with dropping the mold I was able to cast some good portals consistently.

 

I'll go over some of the key findings here.

 

Woodland Scenic Light Weight Hydrocal has a problem.

 

It appears that the mix separates during shipping. Although the instructions states to "shake the box for 30 seconds before use" it appears that the mix remains separated. It was made evident when I consumed the second box of hydrocal. I noticed that the casting were getting hot during the curing process. In the previous casting the hydrocal never got hot. Before opening the new container of hydrocal I shook it over and over. On the first casting it remains somewhat cold. This is an indication that the shaking is not effective. This will result in some casting being brittle. this may be why some people are dealing with hits and misses.

 

I guess the only remedy is to transfer the hydrocal to a larger container and attempt to mix it there. 

 

Mixing

 

The mixing the hydrocal is a dual action process. The first is allowing the hydrocal to accept or absorb the water. Once the hydrocal has fully accepted the water it will start the second process of reaction. The mixing or agitation of the water soaked hydrocal causes the second element in the mix to react. This reaction is called the kicker. The kick is a chemical reaction that creates heat and the curing process. If the mixture has too much water the kicker will not activate, if the mixture is too dry it cannot take the form of the mold. 

 

This is where the consistency is important.

 

Spray Bottle

 

Using the spray bottle is the best way to control the amount of water applied especially if small batches are needed. This control allows you to dial in the exact consistency that may be required by a particular mold. It is important to note that once the mixing has begun and the kicking process has started you cannot add hydrocal. Remember it is a dual action process. The hydrocal needs time to absorb the water and then it will react to the kicker. Adding water too late into the kicking process will cause the kicking process to break down. .

 

Water Wetter 

 

The correct amount of detergent is important is that it breaks the tension of the water. (Tension is the beading effect of the water). The detergent in the water acts as a bonding agent that allows the water to spread out and not bead up. When you pour the hydrocal into the mold instead of repelling from the mold surface the molecules of the hydrocal will align itself with the contours of the mold. The excess water can either be absorbed in the hydrocal or work with the trapped air. The air bubble surround itself with the excess water and moves its way to the top. 

 

I took Jeff's suggestion of increasing the water wetter mix to 50/50 and it worked. Thanks Jeff!!

 

Using a small spray bottle increases the concentration of the mix faster. Using a detergent with a bold color allows you to see the concentration of the mix. That way you will always have a visual indicator for your mix allowing for adjustments.

 

 

 

Dropping Mold 

 

Placing the mold on a flat board and dropping it will cause the hydrocal to pack itself tighter in the mold. This created a denser casting but most important it caused the air bubbles to move upward. As you drop the mold onto the floor the grains of hydrocal packs itself tighter and tighter and takes on the shape of the mold.

 

If you keep these factors in mind you should be able to cast decent molds.

 

 

Inobu

 

My last test will by to use regular hydrocal and compare is to WS LWH.

Edited July 29, 2016 by inobu