How to make a slip casting pump system

James Pagni

We have all been there using the buckets to pour our slip. Maybe the buckets are heavy or you spill a little more then you want outside of the mold instead of inside it. Well we have your solution and it will be a game changer for you. Do note that you will need to spend around $200 to set this up, but we will make sure to cover the most frugal route possible.
Image result for slip casting pump booth
Now take a look at the bucket above. This in theory is what we will be making but ours wont cost $450. Plus I recommend using a barrel instead of a 6 gallon bucket. It really depends on how much slip you plan on using. Because for a small studio it might be easier to find 5 gallon buckets then a 35 gallon barrel. But if you want a barrel, ask local ceramic shops/studios or any manufacturing facilities because they order many kinds of materials in barrels and then throw them away. That is how we got ours and recommend you do the same. So let us start with a barrel or bucket.
Image result for 35 gallon barrel
 You will want some type of barrel that has a lid that can be removed. As the slip sits, you will need to mix it and therefore, having a lid to reach your mixing drill down into it is a must. Plus it will preserve the slip for many months so it wont dry out. So keep in mind you need to have a metal mixing blade of some kind and the drill. Next we will go over the mechanical components we will need. First will be an air compressor.
See the source image
This is the 3 gallon air compressor we use right now. It is just enough to get the job done and we don't recommend a smaller compressor (unless your using a bucket and want to save money). It can get difficult for the slip to be moved if the air compressor doesn't have the constant amount of pressure needed. We run our air compressor at about 40 PSI for a steady stream. But now we need to talk about the pump that is going to help move the slip, and this compressor feeds air to that pump.
This is a self priming double diaphragm pump. We use this brand called Flowjet and unfortunately the price has gone up a tone on these. You want to be spending around $100 on these kind of pumps but look for sales (look at places like ZORO or Kleen-Ritecorp) because I got mine for about $85. You will have to shop around but as long as it is an air operated double diaphragm pump, it will work perfectly. I have had mine going for 3 years and no problem. Below is one I found on Amazon for about $113 but is a little harder to set up tubing with. Plus I can't recommend this because I've never used it.
As long as the pump can move 5 gallons per minute or more then you should be good. Also pumps can only move liquids so far in distance. For example ours is a 5GPM pump and is only rated to move a little over 20ft of liquids total. Not all pumps will have this listed so just keep that in mind for when we set up our tubing. Before we put it all together let us cover the pump gun.
Image result for fuel pump gun
You can buy these fuel pump guns on Ebay/Amazon or do what I did and look for a local diesel fuel pump supplier (or something like that) where they will have everything used for trucks with on board fuel reserve pump systems. Make sure you get a plastic gun because the metal ones don't like clay. I guess metal will work because I see professional systems being sold with them but I have heard otherwise. So lets get to tubes and hardware so we can hook everything up. Do note that you really should go to a hose supply store for all these parts to make sure they are correct for what you need, anything you can't find, it will be online. Here is the list:
Image result for 1/2 brass male thread to tubing fitting"1/2 Male Pipe Thread Adapter"
(this part is only needed if you buy the blue pump, the black one has the barbed adapter built in)
"1/2 x 1/2 x 3/4 Barb Reducing Tee"
(you'll only need one of these)
"1/4" hose adapter plug compressed air couplings"
(2 of these) 
"3/4 inch Bulkhead Female" (x1)
See the source image "1/2 inch PEX to 3/4 inch Brass Male" (x1)
(make sure this will fit into your bulkhead before you buy it)
Image result for vinyl tubing"1/2 inch and 1/4 inch Vinyl Tubing"
(20ft or less of 1/2")(For the 1/4" tube, 5ft or enough to reach compressor to pump)
(thickness of the tube will determine how stiff the tube is, a thicker tube will prevent kinking, thinner tubes will kink more often, but air compressor hose should be a standard thickness)
  Image result for plummers threading tape"Teflon Tape"
See the source image "Kitchen Sealant"
Image result for hose clamp"Hose clamps"
As you can see above, we will need a handful of components to make this work. It is a bit complex at first sight so hopefully I can make this clear. First we need to drill a hole in the bottom of your barrel or bucket as you see in the picture below. You will want to use a drill and a bit that fits your bulkhead. So I have listed a 3/4" bulk head so you might be able to work with a 3/4" bit. Drill that hole. Then we need to drill another hole closer to the top (about 5 inches down from the top of your barrel or if its a bucket then only do about 2 inches) for the slip to be pumped back into the barrel. This top hole only needs to fit your half inch tube. So drill with a 1/2" bit for that.
   See the source image
"Bulkhead with rubber washer inside and outside" (normally only one washer inside)
Unscrew the nut from the bulkhead and remove the washer. Now since a barrel can hold hundreds of pounds of slip (depending on the size, but buckets may not need this extra sealant step since they can't hold much slip), I don't trust these to prevent leaking (it should though). You can put a thin bead of the silicone kitchen sealant on the inside and outside of the hole you cut. Use some Teflon tape to wrap around the bulkhead threading (look up how to use Teflon tape if you have never used it). Place the bulkhead through the hole, and then go inside your barrel/bucket and put the washer on followed by the nut. Tighten the nut with wrenches, one on the inside nut and one on the outside part. Allow the proper time for the sealant to dry before putting slip in (Read the sealants drying instructions).
Image result for bulkhead in a barrel
"Most bulkheads are plastic, but we recommend using brass to match all other hardware"
Let us go to the air compressor tube that supplies the air to the system. We need a tube that starts at the air compressor so it can feed air to the pump. The tube will be 1/4" vinyl or something similar. You will need two 1/4" hose adapter plug compressed air couplings. You will also need two hose clamps to tighten the hose around the hose adapter part of the brass fitting. Put your clamps on first and then insert the adapter. Finish by tightening the clamps.
Now one part will connect into the compressor port and the other end will be inserted into the pumps air inlet. Onto the 1/2" tubes that will be moving the slip through them. I want to note first, that over time there will be some build up of slip on the inside of the tubes. It wont cause much problem but you will need to turn up your PSI when it sits for some time so it will force it to move along. You can also take it apart ever year or two to clean or even replace them. Quick question, have you ever replaced the fittings on a garden hose? Well this is the exact same thing just with a different type of hose. Look at the example below.
 Select our 1/2 inch PEX to 3/4 inch Brass Male adapter. We will start by wrapping the Teflon tape around the male threading. Using two wrenches, tighten the male fitting into the female bulkhead. Then as you see, you have the hose clamp on first and then force the fitting into the tube. (Our male adapter will be in place of where you see the garden hose attachment being inserted) Once its in there, tighten the clamp. From here, our tube will run to the inlet port of our pump. You want to have your pump as close to your barrel/bucket so you don't have to run much tubing(mine is about 2 feet long). So this is where you have to decide if you need to hook up the 1/2" Male Pipe Thread Adapter, or just run the tube right into the pump and clamp down. If you do need to hook that up it will be the exact same way as the last step. Start with the Teflon Tape.
Image result for teflon tape
You will need to do this for the inlet and outlet if using the blue pump style. As you can see in the picture below, in order to hook up to their pump they had to screw two threaded pipe adapters at the top outlet, and the bottom inlet ports. Again just remember to use Teflon tape around your adapters threading, then tighten them in using wrenches. Get your tube that is connected to your bulkhead and cut it to the length needed to reach your pump. Put the hose clamp on and slide the tube over the barbs of the inlet port. Tighten the hose clamp. (Like the table below with the pump secured to the table, this is how I suggest setting your system up with it secured and your barrel right up above on the table too)
See the source image
Our next part will be to incorporate our barb reducing T so we can hook up the pump gun. So lets start with the pump gun. The tube that attaches to the bottom of the gun is usually going to be a 3/4" tube. That is why you need the 3/4" to 1/2" Tee. Same concept, get 1 foot of 3/4" vinyl tubing. Add two hose clamps to each end, and then force the tube over the guns barbs and tighten the clamp. Then put the tube onto the brass Tee and tighten that clamp too.
Now from here we will want to run one 1/2" tube from the pump outlet to the brass tee and then another tube from the other side of the tee into the top hole we cut in our barrel/bucket. I ran my tube from the pump to the tee at about 8 feet and then from the tee to the barrel at about 10 feet (length will depend on your studio and how far your molds are away from the pump). Same thing applies, put your hose clamps on, then slide the hose over the barbs, and then tighten the clamps. FYI, these fittings are used for PEX plastics. Just keep in mind, you want this system to be a continued loop, so as long as it look like it will send all of your slip back into the barrel then your good to use this (other then when you pull the gun trigger, then it will flow out).
I am giving you this guide so you know the concept but it really comes down to your budget and needs. So all hardware can be adjusted to your needs or liking (you could even be able to get away with plastic hardware instead of brass but you risk breakage at the exchange of cheaper parts).  When it comes to the pumps, there are single and double diaphragm pumps. As it sounds, the double diaphragm has two diaphragms where as the standard has one. I only know a little about these pumps so do your own research, but it sounds like you will have half the power with a single. It will pump half as far in distance and might not like handling our thick slip. Also metal pumps might not be corrosion resistant like the plastic pumps such as our FlowJet. So try for the double but it's all on you.
Diaphragm Pump Action diagramImage result for diagram of double diaphram pump
  "Single Diaphragm"      "Double Diaphragm"
That is it, and boy what a difficult post this was to do. I didn't realize how complicated this was until I thought back to me spending an hour in the hosing store trying to figure it out. So your welcome in advance 😉, and in exchange all I ask is that you share the results of your set up with me using some pictures. Email them or send them to me on social media @ceramicsmokeware  
Hard to see but this is mine

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