Introduction
Substrate is the variable most print operations control completely and plan for least. The press is fixed, the artwork is fixed, the deadline is fixed — but the stock is a choice, and it changes feed reliability, ink consumption and finished color all at once.
On a production inkjet envelope press, getting that choice right is the difference between a clean 20,000-piece run and a morning spent chasing double-feeds.
Key Takeaways
- Every press has a hard maximum feed thickness — check it before ordering stock
- Absorbency drives dot gain, which drives apparent density and color
- Pigment-based HP ink is water, fade and scratch resistant
- Only the 1175 Pro + PXG handles packaging substrates
- Feeder type affects which stocks run reliably at speed
- Qualify any new substrate with a sample run before committing to a job
The Hard Limits: Thickness And Size
Start here, because no amount of color management fixes a substrate that will not feed.
| Press | Max feed thickness | Feed size |
|---|---|---|
| HP iJetColor 1175 | 1/8" | Up to 11.75" x 17" |
| HP iJetColor 1175C | 3/8" | 3" x 3.5" to 12" x 17" |
| HP iJetColor 1175 Pro + PXG (envelopes) | 3/8" | 2" x 3.5" to 12" x 17" |
| HP iJetColor 1175 Pro + PXG (packaging) | 1/2" | Up to 14" x 20" |
| HP iJetColor 1275 Pro | — | 12" x 14"; images every envelope size up to 12.75" |
Maximum print area is 11.7" x 17" on the 1175, 1175C and 1175 Pro + PXG. The 1275 Pro has a maximum print width of 12.7".
Note the jump between the 1175 at 1/8" and the 1175C at 3/8". If your job mix includes heavier or padded stock, that difference decides which press you need.
Absorbency, Dot Gain And Density
Inkjet lays fluid ink onto a surface. What the surface does with that fluid determines how the job looks.
Absorbent, uncoated stock pulls ink into the fibres. The dot spreads, which is dot gain. Apparent density rises, fine detail softens, and color can shift from what you approved on screen.
Coated or tightly-sized stock holds ink nearer the surface. Dots stay tighter, detail holds, and color reads closer to the profile — but dry-time and handling behavior change.
Kraft and recycled stock vary batch to batch far more than white wove, and that variation shows up as density drift across a long run.
This is why color is managed in the front end. Every press prints full-bleed with PMS color matching from a PDF-based DFE and RIP carrying ICC color profiles. The profile is doing the work of compensating for substrate behavior — but a profile built for one stock does not automatically serve another.
Why Pigment Ink Matters Here
All five iJetColor products use pigment-based HP ink that is water, fade and scratch resistant, jetted through HP thermal inkjet printheads: an HP TIJ 4.0 108 mm CMYK printbar on the 1275 Pro, and the HP FI-1000 PageWide printhead on the 1175, 1175C and 1175 Pro + PXG.
For envelope work that durability is not a luxury. Mail gets sorted mechanically, handled repeatedly and occasionally rained on. Pigment ink sits differently on uncoated stock than dye ink does, and it is the reason output survives the mail stream.
Feeding: The Practical Constraint
Color is a quality problem; feeding is a production problem, and it stops runs.
Each press uses a feeder designed for its class of work:
- The 1275 Pro uses a rotary vacuum pick-up feeder holding up to 1,000 envelopes with roller-based alignment, plus an 8 ft smart exit conveyor with stacker, job and output count, and double-feed detect.
- The 1175 Pro + PXG uses Straight Shooter automated vacuum feeding for envelopes with an integrated PXG feeder for packaging.
- The 1175C and 1175 use a Quick Adjust Feeder; on the 1175C it is automated and integrated with variable speed.
- The 1175 additionally has a full-bleed belt system and industry-leading alignment.
Things that affect feed reliability in practice: stock curl, static in dry conditions, inconsistent flap geometry across a batch, window envelopes with variable patch adhesion, and thickness variation within a single carton of stock.
Packaging Substrates
Only the HP iJetColor 1175 Pro + PXG prints packaging. It handles paper bags, small corrugate and other packaging substrates up to 14" x 20" and 1/2" thick, at 18 inches per second.
Packaging brings different questions from envelopes:
- Surface coating and how it accepts aqueous pigment ink
- Flute or texture profile on corrugate, and how it affects apparent detail
- Pre-existing print or varnish on the blank
- Downstream folding, gluing or filling and whether the print survives it
None of these has a general answer. They have a sample-run answer.
Qualify New Stock Before You Quote It
The reliable method is unglamorous:
- Get the actual stock you intend to buy, from the batch you intend to buy
- Run a representative job, not a test pattern
- Check feed reliability at production speed, not at a crawl
- Check color against your PMS targets
- Check durability through your finishing and mailing process
- Use the iJetColor Flow 2.0 Cost Calculator to convert consumption into a per-piece figure
iJetColor runs live demos from its facility at 2935 Waters Rd, Suite 200, St Paul, MN 55121, and provides sample kits on request. Free nesting envelopes are available with the 1175.
Conclusion
Substrate choice sits upstream of nearly every quality and reliability problem on a production inkjet press. Check thickness against the machine first, understand what absorbency will do to your color second, and qualify anything new with a real run before it appears on a quote.
To test your own stock on a production press, call (800) 456-1400 or request a sample kit.
Frequently Asked Questions
What is the maximum stock thickness these presses handle?
1/8" on the HP iJetColor 1175, 3/8" on the 1175C and for envelopes on the 1175 Pro + PXG, and up to 1/2" for packaging on the 1175 Pro + PXG.
Does uncoated stock print well on production inkjet?
Yes, and it is the norm for envelope work. Uncoated stock is more absorbent, so dot gain increases and apparent density rises. ICC profiles in the DFE and RIP compensate for this, but a profile suited to one stock will not automatically serve another.
How durable is the printed output?
Ink is pigment-based HP ink that is water, fade and scratch resistant. Confirm durability through your specific finishing and mailing process with a sample run.
Can these presses print on paper bags or corrugate?
Only the HP iJetColor 1175 Pro + PXG, which prints paper bags, small corrugate and other packaging substrates up to 14" x 20" and 1/2" thick at 18 inches per second.
Why does my color shift when I change paper?
Because absorbency changes dot gain, which changes apparent density and color. Color is managed through ICC profiles and PMS matching in the RIP, so a substrate change may need profile attention as well as a visual check.
How should I qualify a new substrate?
Run a representative job on the actual stock at production speed, check feed reliability, color against PMS targets and durability through finishing, then use the Flow 2.0 Cost Calculator for a per-piece cost. Sample kits and live demos are available from the St Paul facility.
