post(blog): UV-reactive bed glue PSA (draft, published:false)

src/lib/components/GlueScaler.svelte

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+<script lang="ts">
+	// GlueScaler.svelte — main UV-reactive bed glue (the "specialized" recipe).
+	// Data only; the engine lives in WeightScaler.svelte. 1× ≈ 2 oz (smallest
+	// worthwhile batch); default 2× ≈ 4 oz (recommended minimum).
+	import WeightScaler from './WeightScaler.svelte';
+
+	const ingredients = [
+		{ item: 'PVP-K90 powder', grams: 4.0, role: 'Primary film former — K90 (MW ~1.3M) is the strength upgrade over Frank’s K30' },
+		{ item: 'PVA, 88% hydrolyzed (cold-water grade)', grams: 1.2, role: 'Secondary film former / toughness — pins a minimum water fraction' },
+		{ item: 'PEG-400', grams: 1.0, role: 'Tackifier / plasticizer — the highest-leverage bond-strength additive' },
+		{ item: '1% boric-acid stock solution', grams: 0.85, role: 'Delivers a trace PVA crosslink (~0.7% of PVA) — dosed via stock so it’s weighable' },
+		{ item: 'Coated SrAl₂O₄:Eu,Dy phosphor, 35–50 µm', grams: 2.0, role: 'UV-reactive coverage indicator — MUST be waterproof/encapsulated grade' },
+		{ item: 'Ethanol (≥95%, denatured ok)', grams: 26.5, role: 'Co-solvent for PVP/PEG; flashes off on the heated bed' },
+		{ item: 'Distilled water (free water)', grams: 20.86, role: 'Dissolves the PVA; carrier lands at ~55:45 ethanol:water' }
+	];
+
+	const presets = [
+		{ factor: 1, label: '×1 · ~2 oz' },
+		{ factor: 2, label: '×2 · ~4 oz', recommended: true },
+		{ factor: 4, label: '×4 · ~8 oz' }
+	];
+
+	const footnote =
+		'Solids are ~14.6% by weight (PVP:PVA ≈ 77:23). 1× is the smallest worthwhile batch; 2× (~4 oz) is the recommended minimum. A 0.01 g scale is assumed — the boric acid is dosed as a 1% stock because the neat mass (≈8 mg) is below that resolution.';
+</script>
+
+<WeightScaler title="Glue batch scaler (by weight)" {ingredients} {presets} defaultFactor={2} {footnote} />

src/lib/components/GlueScalerPinch.svelte

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+<script lang="ts">
+	// GlueScalerPinch.svelte — "in a pinch" simplified derivation from on-hand
+	// chemicals (PVP-40, PVA powder, 91% IPA, distilled water, heavy PEG/PEO,
+	// plain strontium aluminate). 1 oz base; presets are absolute mini sizes.
+	// Still stronger than Frank's via the PEG/PEO tack lever + slightly higher
+	// adhesive solids — no K90, no boric acid, no coated phosphor required.
+	import WeightScaler from './WeightScaler.svelte';
+
+	// 1× = 1 oz ≈ 28.35 g finished glue.
+	const ingredients = [
+		{ item: 'PVP-40 powder (K-30 class, MW ~40k)', grams: 2.8, role: 'Film former — same PVP grade as Frank’s; the backbone' },
+		{ item: 'PVA lab powder', grams: 1.1, role: 'Toughness (PVP:PVA ≈ 72:28, echoes Frank’s 70:30)' },
+		{ item: 'PEG/PEO powder (heavy MW)', grams: 0.5, role: 'Tackifier — the strength edge over Frank’s; potent & stringy, start low' },
+		{ item: 'Strontium aluminate (plain, uncoated)', grams: 1.0, role: 'UV coverage indicator — uncoated, so mix small & use fresh' },
+		{ item: '91% isopropyl alcohol', grams: 16.0, role: 'Carrier; flashes off. Kept IPA-heavy to slow phosphor hydrolysis' },
+		{ item: 'Distilled water', grams: 6.95, role: 'Just enough to dissolve the PVA (carrier ≈ 63:37 IPA:water)' }
+	];
+
+	const presets = [
+		{ factor: 1, label: '1 oz' },
+		{ factor: 2, label: '2 oz' },
+		{ factor: 4, label: '4 oz' }
+	];
+
+	const footnote =
+		'Adhesive solids ~15.5% (PVP+PVA+PEO), a touch above Frank’s — the PEG/PEO is the tack lever. Uncoated phosphor hydrolyzes in water over time, so mix mini batches and use fresh; shake before each use. Heavy PEO strings — if your applicator clogs or cobwebs, cut the PEO. A 0.01 g scale is assumed.';
+</script>
+
+<WeightScaler
+	title="In-a-pinch batch scaler (on-hand chemicals)"
+	{ingredients}
+	{presets}
+	defaultFactor={1}
+	{footnote}
+/>

src/lib/components/WeightScaler.svelte

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+<script lang="ts">
+	// WeightScaler.svelte — generic by-weight batch scaler engine.
+	//
+	// Recipe data lives in thin wrapper components (GlueScaler, GlueScalerPinch)
+	// so the wrappers can be dropped into the mdsvex blog without tripping its
+	// brace-escaper. Everything is grams for a 0.01 g scale, with a g <-> oz
+	// toggle. `factor` multiplies the base-batch grams.
+
+	type Ingredient = { item: string; grams: number; role: string };
+	type Preset = { factor: number; label: string; recommended?: boolean };
+
+	let {
+		title = 'Batch scaler (by weight)',
+		ingredients = [],
+		presets = [{ factor: 1, label: '×1' }],
+		defaultFactor = presets[0]?.factor ?? 1,
+		totalLabel = 'Finished glue',
+		footnote = ''
+	}: {
+		title?: string;
+		ingredients?: Ingredient[];
+		presets?: Preset[];
+		defaultFactor?: number;
+		totalLabel?: string;
+		footnote?: string;
+	} = $props();
+
+	const G_PER_OZ = 28.349523125;
+
+	// null = "follow the recipe's default"; a click pins an explicit factor.
+	let factorOverride = $state<number | null>(null);
+	const factor = $derived(factorOverride ?? defaultFactor);
+	let unit = $state<'g' | 'oz'>('g');
+
+	const rows = $derived(
+		ingredients.map((ing) => {
+			const grams = ing.grams * factor;
+			const amount = unit === 'oz' ? (grams / G_PER_OZ).toFixed(3) : grams.toFixed(2);
+			return { item: ing.item, role: ing.role, amount };
+		})
+	);
+
+	const totalGrams = $derived(ingredients.reduce((s, i) => s + i.grams, 0) * factor);
+	const totalOz = $derived(totalGrams / G_PER_OZ);
+</script>
+
+<div class="card p-4 preset-outlined-surface-500 not-prose my-6">
+	<div class="mb-3 flex flex-wrap items-center justify-between gap-3">
+		<h3 class="m-0 text-lg font-semibold">{title}</h3>
+		<div class="flex items-center gap-2">
+			<div class="flex gap-1" role="group" aria-label="Scale the batch size">
+				{#each presets as p (p.factor)}
+					<button
+						type="button"
+						class="badge {factor === p.factor
+							? 'preset-filled-primary-500'
+							: 'preset-outlined-surface-500'}"
+						aria-pressed={factor === p.factor}
+						aria-label={`Batch ${p.label}${p.recommended ? ', recommended minimum' : ''}`}
+						onclick={() => (factorOverride = p.factor)}
+					>
+						{p.label}{p.recommended ? ' ✓' : ''}
+					</button>
+				{/each}
+			</div>
+			<button
+				type="button"
+				class="badge preset-outlined-surface-500"
+				aria-pressed={unit === 'oz'}
+				aria-label="Toggle grams or ounces"
+				onclick={() => (unit = unit === 'g' ? 'oz' : 'g')}
+			>
+				{unit === 'g' ? 'grams' : 'ounces'}
+			</button>
+		</div>
+	</div>
+
+	<table class="w-full text-sm">
+		<caption class="sr-only">
+			{title}, ~{totalOz.toFixed(1)} oz, shown in {unit === 'g' ? 'grams' : 'ounces'}
+		</caption>
+		<thead>
+			<tr class="text-left text-surface-600 dark:text-surface-400">
+				<th scope="col" class="py-1 pr-3 font-medium">Weight</th>
+				<th scope="col" class="py-1 font-medium">Ingredient</th>
+			</tr>
+		</thead>
+		<tbody>
+			{#each rows as row (row.item)}
+				<tr class="border-t border-surface-300 dark:border-surface-700">
+					<td class="whitespace-nowrap py-1 pr-3 font-mono">{row.amount} {unit}</td>
+					<td class="py-1">
+						<span class="font-medium">{row.item}</span>
+						<span class="block text-xs text-surface-500">{row.role}</span>
+					</td>
+				</tr>
+			{/each}
+			<tr class="border-t-2 border-surface-400 dark:border-surface-600 font-semibold">
+				<td class="whitespace-nowrap py-1 pr-3 font-mono">
+					{unit === 'oz' ? totalOz.toFixed(3) : totalGrams.toFixed(2)}
+					{unit}
+				</td>
+				<td class="py-1">{totalLabel} (~{totalOz.toFixed(1)} oz)</td>
+			</tr>
+		</tbody>
+	</table>
+
+	{#if footnote}
+		<p class="mt-3 text-xs text-surface-500">{footnote}</p>
+	{/if}
+	<p class="sr-only" aria-live="polite">Showing ~{totalOz.toFixed(1)} oz in {unit === 'g' ? 'grams' : 'ounces'}.</p>
+</div>

src/posts/2026-06-06-uv-reactive-bed-glue.md

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+---
+title: "Bed glue you can see in UV (and a Klipper gate that won't print without it)"
+date: "2026-06-06"
+description: "A 3D-printer bed adhesive stronger on paper than Frank's Instagoo, infused with strontium-aluminate phosphor so a 365 nm flash shows coverage — with a by-weight batch scaler, an off-the-shelf UV sensing BOM, and a Klipper pre-print gate."
+tags: ["3d-printing", "klipper", "chemistry", "adhesives", "strontium-aluminate", "uv", "phosphor", "diy", "maker", "recipe"]
+category: "tutorial"
+published: false
+slug: "uv-reactive-bed-glue"
+excerpt: "Stronger-on-paper PVP/PVA bed glue dosed with strontium-aluminate phosphor, a by-weight batch scaler, a Mouser UV-sensing BOM, and a Klipper macro that aborts on a bare bed."
+---
+
+<script>
+	import GlueScaler from '$lib/components/GlueScaler.svelte';
+	import GlueScalerPinch from '$lib/components/GlueScalerPinch.svelte';
+</script>
+
+[Frank's "Instagoo"](https://goo.by.frank.af/) is a tidy 3D-printer bed glue: 21 g PVP-K30 + 9 g PVA in 200 ml of ~50% isopropyl alcohol — a 70:30 PVP:PVA solution at roughly 15% solids. It's the same chemistry family as the [DIY "Super Goop"](https://hackaday.com/2022/12/06/homebrew-3d-printer-goop-promises-better-bed-adhesion/) lineage and the commercial brush-ons: [Vision Miner Nano](https://visionminer.com/products/nano-polymer-adhesive)'s SDS discloses only an IPA carrier and a trade-secret polymer, and [Luke's Laboratory](https://www.lukeslabonline.com/products/bed-adhesive) sells Standard/Double/Triple "strength," which is just the same liquid at different solids. None of them publishes a real bond number.
+
+I wanted two things on top: glue that is **stronger**, and glue I can **see** 👀. The seeing part is the fun bit — dose it with strontium-aluminate phosphor and a coat lights up green under UV, so a sensor (and a Klipper macro) can check the bed is actually covered before a print starts.
+
+Fair warning up front: the "stronger" claim here is mechanistic, not yet measured. I haven't put a force gauge on a peel test — that's the next post. What follows is three changes each backed by a named source, which is the most I'll assert until I have numbers.
+
+The full build — BOM, wiring, the Klipper config and host script — lives at **[transscendsurvival.org/tinyland-goo](https://transscendsurvival.org/tinyland-goo/)**. This post is the short version.
+
+## The recipe
+
+Everything by weight, for a 0.01 g scale. 1× (~2 oz) is the smallest worthwhile batch; **2× (~4 oz) is the recommended minimum**, so that's the default below.
+
+<GlueScaler />
+
+## Three honest knobs
+
+Each of these is a documented lever, not a hunch:
+
+| Knob | Change | Why it should help | The number to watch |
+| --- | --- | --- | --- |
+| Film former | PVP-K30 → [PVP-K90](https://ulipolymer.com/difference-between-pvp-k30-and-pvp-k90/) | ~30× the molecular weight (~1.3M vs ~40k) → more viscosity, film cohesion, tack | it's a drop-in swap |
+| Tackifier | add PEG-400 | pressure-sensitive tack in [PVP/PEG blends peaks near 36 wt% PEG](https://www.tandfonline.com/doi/abs/10.1080/00218460213491) | start at ~20% so the film still releases |
+| Crosslink | trace boric acid | [boric acid bonds PVA](https://iopscience.iop.org/article/10.1088/2631-8695/ad4cb4) for cohesion while staying water-redispersible | keep it ≤1% of the PVA — past that it stops releasing |
+
+That last row is the one number worth getting right: enough crosslink to stiffen the film, not enough to weld your print to the bed.
+
+## The catch: strontium aluminate hates water
+
+`SrAl₂O₄:Eu,Dy` excites across UV-A (peak ~365 nm) and [emits green at ~520 nm](https://en.wikipedia.org/wiki/Strontium_aluminate) — that's the whole trick. But bare phosphor [hydrolyzes in water](https://www.sciencedirect.com/science/article/abs/pii/S0254058407003719) to non-luminescent hydroxides and quietly stops glowing. You can't dodge it by going anhydrous, because the PVA needs water to dissolve. The fix is a silica/fluoride-coated ("waterproof") grade plus a modest water fraction. Coated powder is mandatory here, not a nicety.
+
+It's non-toxic with no GHS hazard class, but it's a hard mineral dust — mask and gloves when weighing.
+
+## In a pinch
+
+The recipe above wants PVP-K90, an encapsulated phosphor, and a boric-acid crosslink — specialized stock that's still in the mail. So here's a derivation from what's already on the shelf: PVP-40, PVA lab powder, 91% IPA, distilled water, a heavy PEG/PEO powder, and plain strontium aluminate. It's for an automated applicator on **less mission-critical** printers, in 1/2/4 oz mini batches.
+
+It still beats Frank's — same PVP/PVA backbone, a hair more solids, and the PEG/PEO tackifier doing the heavy lifting instead of K90 + crosslink. Two honest trade-offs: the uncoated phosphor hydrolyzes over time (mix small, use fresh), and heavy PEO is stringy (keep it low or the applicator cobwebs). Both glues read the same under UV.
+
+<GlueScalerPinch />
+
+## Seeing coverage
+
+Flood the bed with 365 nm UV and read the green that comes back. An [AMS AS7341 spectral sensor](https://www.adafruit.com/product/4698) has channels at 515 nm and 555 nm straddling the phosphor peak, and its on-chip interference filters reject the 365 nm excitation — so a single-point read often needs no separate glass filter. Baseline the bare bed once; coverage is the green rise above it. The whole sensing BOM (OSRAM 365 nm LED, MEAN WELL driver, the sensor, a Pi) is on the [project page](https://transscendsurvival.org/tinyland-goo/).
+
+## The Klipper gate
+
+`PRINT_START` runs a host script (via the `gcode_shell_command` extension) that reads the sensor and writes the result back through Moonraker's `SAVE_VARIABLE`. A second macro reads that value and aborts — before any heating or motion — if coverage is too low:
+
+```toml
+[gcode_macro _COVERAGE_GATE]
+gcode:
+    {% set min_cov = params.MIN_COVERAGE|default(70)|float %}
+    {% set cov = printer.save_variables.variables.coverage_pct|default(-1)|float %}
+    {% if cov < min_cov %}
+        { action_raise_error("COVERAGE GATE: %.1f%% < %.1f%%. Re-glue and restart." % (cov, min_cov)) }
+    {% endif %}
+```
+
+Two-point calibration (bare bed → 0%, fully glued → 100%) is required. The complete `coverage_gate.cfg` and `coverage_gate.py` are in the [tinyland-goo repo](https://github.com/Jesssullivan/tinyland-goo).
+
+## Safety, briefly
+
+Flammable alcohol carrier (mix away from flame; let it flash off before the bed heats) · phosphor dust (N95/P2 + eye protection when weighing) · boric acid (reproductive hazard if ingested — gloves, away from food) · 365 nm UV-A (eye/skin hazard at power; enclose it and pulse only during the read).
+
+Next time, hopefully, with a force gauge and actual peel numbers. Until then it glows, which is most of the fun anyway.
+
+Cheers, -Jess