Question for those with Alginate experience

Makrel Johnson

New Member
I'm working on a head casting and I'm having a little trouble with the Smooth-On Alginate. I can't seem to get that happy medium where it's mixed smooth enough, I'm using a squirrel cage mixer, and thick enough to hold a face while sitting up.

It seems when I mix it thicker, it sets MUCH faster and tends to be lumpier as it's scooped and applied. Mixing enough for it to be smooth has it running off my face and all over the drop cloth.

Anyone experiment with using bottled water? I've read that hard water can make it lumpy and I've got a water softener for the house but I can't seem to get a good feel of it.

I'm planning to use the alginate to get a rough mold to slosh some ultracal 30 in, then make a silicone mold of the cleaned up casting. I have about 3-5 lbs left and I don't want to waste it if it's my prep or technique.

Is there something blatant that I'm doing wrong or is it more trial & error?

Thanks,
Mak
 
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What is the room temp when using it? Too warm or cold and you get poor results.

It's in the basement so it's in the mid to low 60's so I suspect my water might have been on the warm side. The alginate wasn't really cold to the skin.

From their Tech Bulletin:
Mix Ratio: 1 Part Warm Water (80° F / 27° C) to 1 Part Alja-Safe Powder By Volume (or 4 parts water to 1 part Alja-Safe by weight)

I'm pretty sure it wasn't 80° so I'll snag some obviously cold water and give that a go.
 
Hello - new to RPF but have experience with alginate:

I'm assuming this is your first time using it (and if not, my bad and no big deal either way), but alginate does not need to be as "smooth" like you would want for Ultracal or Hydracal - while the surface may appear "bumpy", the curing side underneath will still retain fine details as it is setting. I've always mixed alginate by hand for life casts with no problems. Maybe try to mix up a batch without the mixer? This may be needless to say too, but make sure you're adding water to the alginate and not the other way around (opposite of how you would mix Ultracal).
As others have stated also, cooler water will help as far as the set time goes.
Hope this helps and good luck!
 
Johnson! I was in the same boat as you! I ordered up some smooth-on alginate and ended up using 3 lbs of it trying to cast my friends face.

It didn't seem to matter how close to room temperature I had it or using colder water(even used bottled water thinking my tap water wasn't good)…it always cured too soon.

So after an INSANELY amount of errors, and not having enough to make a good mold, I walked to our local art store, bought some no name alginate for 20 bucks and made a perfect mold. I used tap water, mixed it by hand and had more time to lay it down before it cured.

So, i'm not sure if it's actually something that you're doing wrong, might have something to do with the smooth on….anyone else have issues with it?
 
Are you mixing alginate into the water or the water into the alginate, you need to do the latter, i also mix mine with a small electric hand whisk to get it smooth, the lower the water temprature , the longer the work time, also check on the setting time on the container , make sure you have not bought the fast set variety of alginate. There is also a product available from artmolds called algislo that is a realy good alginate retarder and bonder that can be very useful.
 
Thanks everyone for the tips. I'm going to try again tonight or tomorrow.

Before:
I was adding equal measured amounts by volume to a single container at once and using the squirrel cage mixer on a drill to mix. BTW - I've learned not to use that kind of mixer to mix anything that 'sets' or you'll get only one use out of it :) A jiffy mixer with the 2 blades looks MUCH easier to peel material off of.

Also, last night I discovered my water softener was completely empty (of salt) and I think that may have been a contributing factor. My water is really hard out here and when I mix next, I'll try some COLD, filtered water added to the measured alginate to see how it goes.

Thanks Again,
Mak
 
Couple things...

Cool water. Water temp makes all the difference, same with mineral content. If you are iffy about your tap water, buy distilled water. Same thing when mixing your Ultracal or Hydrcal plaster, it makes a difference.

Hand mix this stuff, mechanically mixing causes a faster reaction with Smooth-On's alginate formula. The set time is also 8 minutes, which is middle of the road when it comes to set times. Some cheap powdered cottage cheese mix they pass off as Alginate takes like 20 minutes to set. Mix smaller batches, have alginate retarder handy. Use a Baking Soda & water mix to inhibit the surface so you can patch/ build up properly.
 
I do not have a lot of experience with the smooth on alginate, but I do use alginate a lot...
Just a different brand..
I always mix by hand...
I always like to keep some alginate bonder handy as well..

When I do it, I weigh out my components..
72 grams of alginate.
To about 200 ml. Of water.. And the water is usually around 70 degrees f.
I also like to keep a rasp file handy... A little hand rasp, pop the little end off of the plastic handle, and keep it on the counter. After the alginate is set, if you have bumps and high points? Use the teeth of the metal rasp to remove the high points. Be careful not to take too much off... Just the high points. Works well to help smooth out the alginate a surface prior to the bandage application .

If I need it thicker, or thinner? Try 70grams of alginate for thinner... Or 75 grams of alginate per 200 ml. For thicker ..

For a face.. Try a 5x batch...
For a full head? A 10x batch...
 
another vote for hand mixing. Whisks or something that your mum would use for cake. the squirrel cage mixer creates heat in the slurry, and heat is alginate's enemy.
 
Are you mixing alginate into the water or the water into the alginate, you need to do the latter,

I have to disagree with you here-- I have used hundreds of pounds of various alginates and NEVER add the water into the alginate-- always the alginate into the water. Never had a problem as I keep it mixing as I am adding.
 
I do not have a lot of experience with the smooth on alginate, but I do use alginate a lot...
Just a different brand..
I always mix by hand...
I always like to keep some alginate bonder handy as well..

When I do it, I weigh out my components..
72 grams of alginate.
To about 200 ml. Of water.. And the water is usually around 70 degrees f.
I also like to keep a rasp file handy... A little hand rasp, pop the little end off of the plastic handle, and keep it on the counter. After the alginate is set, if you have bumps and high points? Use the teeth of the metal rasp to remove the high points. Be careful not to take too much off... Just the high points. Works well to help smooth out the alginate a surface prior to the bandage application .

If I need it thicker, or thinner? Try 70grams of alginate for thinner... Or 75 grams of alginate per 200 ml. For thicker ..

For a face.. Try a 5x batch...
For a full head? A 10x batch...


If you let the alginate harden enough to rasp it off---How do you attach the plaster mother mold????
 
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